Jason has one secret hideout which is simply a playground made of tires.
Specifically of Batmobile tires.
It took him 2 years, 64 family visits and 12 sleepovers but he did it.
The part he's most proud of is that it's undercover as a tire shop. Conveniently on the way to Wayne Enterprises. Bruce passes by this area at least four times a week in daylight.
Bruce's spares of spares don't exist anymore. Robins could be bouncing on hundreds of tires any day of the week. Gotham city has at least two dozen cars acquired in Battires.
But Bruce has no idea. Not a clue. Jason ensures he will never have.
And also that he bounces whenever Bruce passes by.