Vague recollections from when the illusion had hold on him inform him on what at least playground is, though he can make guesses for reservoir tunnel, and how that won't be as useful here. There's no large bodies of water nearby, and any tunnel he's seen has been with a small entrance, but...

"Growmon! Are you good at pretending to sleep?"

He has an idea, and from the alleyway's far end, pauses to look both directions. People are present to both sides of the street, but not in a way that matters for them: they're distracted elsewise, and he waves them all on as he darts diagonally for the next alley that looks wide enough. This way heads toward the central-ish park.