Z - Lost City of Z

The Lost City of Z is the name given by Col. Percy Harrison Fawcett, a British surveyor, to an indigenous city that he believed had existed in the jungle of the Mato Grosso state of Brazil. Based on early histories of South America and his own explorations of the Amazon River region, Fawcett theorized that a complex civilization once existed there, and that isolated ruins may have survived.

Fawcett found a document known as Manuscript 512, held at the National Library of Brazil, believed to have been written by Portuguese bandeirante João da Silva Guimarães. According to the document, in 1753, a group of bandeirantes discovered the ruins of an ancient city that contained arches, a statue and a temple with hieroglyphics. He described the city ruins in great detail without giving its location. Manuscript 512 was written after explorations made in the sertão of the province of Bahia. Fawcett intended to pursue finding this city as a secondary goal after "Z". He was preparing an expedition to find "Z" when World War I broke out and the British government suspended its support.

Y - Year Without a Summer

The year 1816 is known as the Year Without a Summer (also the Poverty Year and Eighteen Hundred and Froze To Death) because of severe climate abnormalities that caused average global temperatures to decrease by 0.4–0.7 °C (0.72–1.3 °F). Summer temperatures in Europe were the coldest on record between the years of 1766–2000. This resulted in major food shortages across the Northern Hemisphere.

Evidence suggests that the anomaly was predominantly a volcanic winter event caused by the massive 1815 eruption of Mount Tambora in April in the Dutch East Indies (known today as Indonesia). This eruption was the largest in at least 1,300 years (after the hypothesized eruption causing the extreme weather events of 535–536), and perhaps exacerbated by the 1814 eruption of Mayon in the Philippines. The Year Without a Summer was an agricultural disaster. Historian John D. Post has called this "the last great subsistence crisis in the Western world". The climatic aberrations of 1816 had greatest effect on most of New England, Atlantic Canada, and parts of western Europe.

X - Xavier Dupont de Ligonnès

The Dupont de Ligonnès murders and disappearance involved the murder of five members of the same family in Nantes, Loire-Atlantique, France, followed by the disappearance of the patriarch of the family, Xavier Dupont de Ligonnès. His wife Agnès Dupont de Ligonnès and their four children were murdered at an undetermined date in early April 2011, and their bodies were found buried in their garden on 21 April. Xavier disappeared at the same time and has not been found. The exact nature of the events have never been determined, but Xavier is the subject of an international arrest warrant and is considered the prime suspect in the murders.

In June 2013, a body was found 20 kilometres (12 miles) from where Xavier Dupont de Ligonnès was last seen. An autopsy was carried out and did not completely exclude the possibility of the body being that of Xavier. The prosecutor in Draguignan, Danielle Drouy-Ayral, stated "at this moment in time, it is not the body of Xavier Dupont de Ligonnès", without providing any more details to explain this declaration.

W - Will-o'-the-wisp

In folklore, a will-o'-the-wisp, will-o'-wisp or ignis fatuus (Latin for 'giddy flame'; plural ignes fatui) is an atmospheric ghost light seen by travelers at night, especially over bogs, swamps, or marshes. The phenomenon is known in English folk belief, English folklore, and much of European folklore by a variety of names, including jack-o'-lantern, friar's lantern, hinkypunk, and hobby lantern, and is said to mislead travelers by resembling a flickering lamp or lantern. In literature, will-o'-the-wisp metaphorically refers to a hope or goal that leads one on but is impossible to reach, or something one finds sinister and confounding.

Will-o'-the-wisp appears in folk tales and traditional legends of numerous countries and cultures; notable will-o'-the-wisp include St. Louis Light in Saskatchewan, The Spooklight in southwestern Missouri, Marfa lights of Texas, the Naga fireballs on the Mekong in Thailand, the Paulding Light in Upper Peninsula of Michigan and the Hessdalen light in Norway. While urban legends, folklore, and superstition typically attribute will-o'-the-wisps to ghosts, fairies, or elemental spirits, modern science explains them as natural phenomena such as bioluminescence or chemiluminescence, caused by the oxidation of phosphine (PH3), diphosphane (P2H4), and methane (CH4) produced by organic decay.

V - Vanishing Hitchhiker

The vanishing hitchhiker (or variations such as the ghostly hitchhiker, disappearing hitchhiker, phantom hitchhiker) is an urban legend in which people travelling by vehicle, meet with or are accompanied by a hitchhiker who subsequently vanishes without explanation, often from a moving vehicle.

Public knowledge of the story expanded greatly with the 1981 publication of Jan Harold Brunvand's non-fiction book The Vanishing Hitchhiker. In his book, Brunvand suggests that the story of The Vanishing Hitchhiker can be traced as far back as the 1870s and has "recognizable parallels in Korea, Tsarist Russia, among Chinese-Americans, Mormons, and Ozark mountaineers." Similar stories have been reported for centuries across the world.

A common variation of the above involves the vanishing hitchhiker departing as would a normal passenger, having left some item in the vehicle, or having borrowed a garment for protection against the cold. The vanishing hitchhiker may also leave some form of information that encourages the motorist to make subsequent contact. In such accounts of the legend, the garment borrowed is often found draped over a gravestone in a local cemetery.

U - UFOs

An unidentified flying object (UFO) is any aerial phenomenon that cannot immediately be identified or explained. Most UFOs are identified on investigation as conventional objects or phenomena. The term is widely used for claimed observations of extraterrestrial spacecraft. 

The term "UFO" (or "UFOB") was coined in 1953 by the United States Air Force (USAF) to serve as a catch-all for all such reports. In its initial definition, the USAF stated that a "UFOB" was "any airborne object which by performance, aerodynamic characteristics, or unusual features, does not conform to any presently known aircraft or missile type, or which cannot be positively identified as a familiar object". Accordingly, the term was initially restricted to that fraction of cases which remained unidentified after investigation, as the USAF was interested in potential national security reasons and "technical aspects" (see Air Force Regulation 200-2).

During the late 1940s and through the 1950s, UFOs were often referred to popularly as "flying saucers" or "flying discs". The term UFO became more widespread during the 1950s, at first in technical literature, but later in popular use. UFOs garnered considerable interest during the Cold War, an era associated with a heightened concern for national security, and, more recently, in the 2010s, for unexplained reasons.

T - Tuanaki

Tuanaki or Tuanahe is the name of an anecdotal vanished group of islets, once part of the Cook Islands. It was located south of Rarotonga and within two days sail of Mangaia. In 1916, the Polynesian Society of Honolulu reprinted an account by a sailor who had visited there in 1842, spending six days among the natives. However this account added that two years later in 1844, a schooner of English missionaries had found nothing. Some Tuanakians who had emigrated to Rarotonga allegedly survived. 

The 1916 publication re-ignited interest in the flyaway islands, and explorer Sir Ernest Shackleton, when planning the Shackleton-Rowett Expedition of 1921–1922, proclaimed as one of his goals the rediscovery of Tuanaki. The explorer died in Antarctic waters before he was able to mount a serious search for the vanished archipelago. It was suggested in 1952 that the Haymet Rocks were a remnant of Tuanaki. However, the existence of the Haymet Rocks at some point is unconfirmed as well.

S - St. Elmo's Fire

St. Elmo's fire is a weather phenomenon in which luminous plasma is created by a corona discharge from a sharp or pointed object in a strong electric field in the atmosphere (such as those generated by thunderstorms or created by a volcanic eruption). It is named after St. Erasmus of Formia (also called St. Elmo, one of the two Italian names for St. Erasmus, the other being St. Erasmo), the patron saint of sailors. The phenomenon sometimes appeared on ships at sea during thunderstorms and was regarded by sailors with religious awe for its glowing ball of light, accounting for the name. Sailors may have considered St. Elmo's fire as a good omen (as a sign of the presence of their patron saint).

St. Elmo's fire is a bright blue or violet glow, appearing like fire in some circumstances, from tall, sharply pointed structures such as masts, spires, and chimneys, and on aircraft wings or nose cones. St. Elmo's fire can also appear on leaves and grass, and even at the tips of cattle horns. Often accompanying the glow is a distinct hissing or buzzing sound. It is sometimes confused with ball lightning.

R - Ressad

Ressad or Ress refers to a now lost city and possibly also to a territory that is still unidentified but believed by scholars to have been somewhere within the borders of modern County Limerick in western Ireland, in what was once the territory of the kingdom of the Uí Fidgenti. The name occurs in only a small number of surviving sources, which for this region of Ireland, of once respectable wealth, are generally quite poor.

According to the early tale known as Conall Corc and the Corcu Luigde, Saint Colmán of Cloyne cursed the city of Ressad, which brought down its walls. Only two Kings of Ressad are known from the surviving sources, both probably belonging to the second half of the 10th century.

Q - Quipu

Quipu (also spelled khipu) are recording devices fashioned from strings historically used by a number of cultures in the region of Andean South America. Knotted strings were used by many other cultures such as the ancient Chinese and native Hawaiians, but such practices should not be confused with the quipu, which refers only to the Andean device.

A quipu usually consisted of cotton or camelid fiber strings. The Inca people used them for collecting data and keeping records, monitoring tax obligations, properly collecting census records, calendrical information, and for military organization. The cords stored numeric and other values encoded as knots, often in a base ten positional system. A quipu could have only a few or thousands of cords. The configuration of the quipus has been "compared to string mops." Archaeological evidence has also shown the use of finely carved wood as a supplemental, and perhaps sturdier, base to which the color-coded cords would be attached. A relatively small number have survived.

P - Pag Triangle

Pag Triangle (Croatian: Paški trokut) is a land formation in the shape of an isosceles triangle located near Novalja, a small town on the Croatian island Pag. The triangle has one side measuring approximately 32 metres (105 ft) and two sides both measuring 22 metres (72 ft). It differs from the surrounding area in the fact that the rocks inside the triangle are of different structure than rocks outside the triangle. Croatian Ufologist Stjepan Zvonarić believes it was the site of a UFO landing which heated the rocks to extreme temperatures in the past. This property is unique to the Pag Triangle rocks, and is not found in rocks in the surrounding area.

Since its discovery in 1999, it is estimated that the Pag Triangle has been visited by over 500,000 tourists. It is a protected area of the Town of Novalja. Croatian ufologists have linked the existence of the triangle to a series of UFO sightings in late 20th century over the island of Pag, while some perceive the triangle as a sign of Holy Trinity, sometimes associated with Catholic priest Zlatko Sudac receiving his stigmata during a conversation about the triangle. In early 2009, a road was built connecting the triangle to the nearby village Caska and thus making it more accessible to visitors.

O - Obelisk

An obelisk (/ˈɒbəlɪsk/; from Ancient Greek: ὀβελίσκος obeliskos; diminutive of ὀβελός obelos, "spit, nail, pointed pillar") is a tall, four-sided, narrow tapering monument which ends in a pyramid-like shape or pyramidion at the top. Originally they were called tekhenu by their builders, the Ancient Egyptians. The Greeks who saw them used the Greek term obeliskos to describe them, and this word passed into Latin and ultimately English. Ancient obelisks are monolithic; that is, they consist of a single stone. Most modern obelisks are made of several stones.

Obelisks played a vital role in their religion and were prominent in the architecture of the ancient Egyptians, who placed them in pairs at the entrance of the temples. The word "obelisk" as used in English today is of Greek rather than Egyptian origin because Herodotus, the Greek traveller, was one of the first classical writers to describe the objects. A number of ancient Egyptian obelisks are known to have survived, plus the "Unfinished Obelisk" found partly hewn from its quarry at Aswan. These obelisks are now dispersed around the world, and fewer than half of them remain in Egypt.

N - Naga Fireball

Naga fireballs (Thai: บั้งไฟพญานาค; RTGS: bang fai phaya nak), also known as bung fai phaya nak or "Mekong lights" and, formerly, "ghost lights" are a phenomenon said to be seen annually on the Mekong River. Glowing balls are alleged to naturally rise from the water high into the air. The balls are said to be reddish and to range in size from smaller sparkles up to the size of basketballs. They quickly rise up to a couple of hundred metres before disappearing. The number of fireballs reported varies between tens and thousands per night. The phenomenon is locally attributed to phaya nak, a giant serpent said to live in the Mekong.

The fireballs are most often reported around the night of Wan Ok Phansa at the end of Buddhist Lent in late-October. Naga fireballs have been reported over an approximately 250 kilometre-long section of the Mekong River centered approximately on Phon Phisai in the Phon Phisai District. Fireballs have also been reported rising from smaller rivers, lakes and ponds in the region. The fireballs were called "ghost lights" by locals until the mid-1980s, when the local council officially named them "phaya nak lights". In 2018 one observer noted that, "...the 'age-old' tradition is, actually, 35 years old."

M - Marian Apparition

A Marian apparition is a reported supernatural appearance by Mary, the mother of Jesus, or a series of related such appearances over a period of time. In order to be classified as a Marian apparition, the person or persons who claim to see Mary (the "seers") must claim that they see her visually located in their environment. (If the person claims to hear Mary but not see her, this is known as an interior locution, not an apparition. Also excluded from the category of apparitions are dreams, visions experienced in the imagination, the claimed perception of Mary in ordinarily-explainable natural phenomena, and miracles associated with Marian artwork, such as weeping statues). Believers consider such apparitions to be real and objective interventions of divine power, rather than subjective experiences generated by the perceiving individuals, even in cases where the apparition is reportedly seen by only some, not all, of the people present at the event's location.

Marian apparitions are considered expressions of Mary's ongoing motherly care for the Church. The understood purpose of each apparition is to draw attention to some aspect of the Christian message, given the needs of a particular time and place. Apparitions are often accompanied by other alleged supernatural phenomena, such as medical cures. However, such miraculous events are not considered the purpose of Marian apparitions, but exist primarily to validate and draw attention to the message.

L - Lantern Man

A lantern man is an atmospheric ghost light, in the folklore of The Fens of East Anglia, seen around Wicken Fen and other areas. According to the stories, first collected by folklorist L.F. Newman, the lights, believed to be evil spirits trying to draw victims to their death in the reed beds, were drawn to the sound of whistling and could be evaded by lying face down on the ground with your mouth in the mud. The phenomenon, which seems to be a variation of will-o'-the-wisp folklore, is now dismissed as the result of combustible marsh gas.

A local fisherman recounted to parapsychologist Peter Underwood how he had once thrown himself to the floor to escape the attention of a lantern man which had been drawn to his whistling. Another local man recounted to folklorist L.F. Newman how he had attracted the attention of a lantern man while whistling to his dog while walking on the fen. The man had taken shelter at the home of a friend, who hung out a horn on a long pole to distract the spirit. The following morning the horn was found to have been burnt up.

K - Kryptos

Kryptos is a sculpture by the American artist Jim Sanborn located on the grounds of the Central Intelligence Agency (CIA) in Langley, Virginia. Since its dedication on November 3, 1990, there has been much speculation about the meaning of the four encrypted messages it bears. Of these four messages, the first three have been solved, while the fourth message remains one of the most famous unsolved codes in the world. The sculpture continues to be of interest to cryptanalysts, both amateur and professional, who are attempting to decipher the fourth passage. The artist has so far given four clues to this passage.

The main part of the sculpture is located in the northwest corner of the New Headquarters Building courtyard, outside of the Agency's cafeteria. The sculpture comprises four large copper plates with other elements consisting of water, wood, plants, red and green granite, white quartz, and petrified wood. The most prominent feature is a large vertical S-shaped copper screen resembling a scroll or a piece of paper emerging from a computer printer, half of which consists of encrypted text. The characters are all found within the 26 letters of the Latin alphabet, along with question marks, and are cut out of the copper plates.

J - Jack the Ripper

Jack the Ripper was an unidentified serial killer active in the largely impoverished areas in and around the Whitechapel district of London in 1888. In both the criminal case files and contemporary journalistic accounts, the killer was called the Whitechapel Murderer and Leather Apron.

Attacks ascribed to Jack the Ripper typically involved female prostitutes who lived and worked in the slums of the East End of London whose throats were cut prior to abdominal mutilations. The removal of internal organs from at least three of the victims led to proposals that their killer had some anatomical or surgical knowledge. Rumours that the murders were connected intensified in September and October 1888, and numerous letters were received by media outlets and Scotland Yard from individuals purporting to be the murderer. The name "Jack the Ripper" originated in a letter written by an individual claiming to be the murderer that was disseminated in the media. The letter is widely believed to have been a hoax and may have been written by journalists in an attempt to heighten interest in the story and increase their newspapers' circulation. The "From Hell" letter received by George Lusk of the Whitechapel Vigilance Committee came with half of a preserved human kidney, purportedly taken from one of the victims. The public came increasingly to believe in a single serial killer known as "Jack the Ripper", mainly because of both the extraordinarily brutal nature of the murders, and media coverage of the crimes.