This resonates with me. Secret gardens are everywhere if you look. For me, in Cleveland, in the 90s it was the `Temple of Lost Love` beneath the Eagle St. Bridge in the Flats. It attracted art of all types, delinquents, prep students, you name it. A place to go for privacy or camaraderie. The saddest day was in the early 00's when it was painted over, fenced off, and patrolled.

EDIT: P.S. Hannu Rajaniemi is an amazing author. `Quantum Thief` is one of my favorite books.