A vestibule is a lobby, entrance hall, or passage between the entrance and the interior of a building. -Wikipedia
Looking at the gate on Broadway a few blocks away from it, we already knew the park was there. Seeing through the gate over the park at the end of the road, we felt the park had come to us too fast and naked. The thin gate was standing still there whispering very low that we were about to cross the intangible boundary. We trespassed. Everything happened so fast and painless.
Thinking about Folly, we imagined a never realized vestibule that should have captured the grand moment of entering into the park.