40 years makes for a long less-than-urban flânerie :)

What are the modern equivalents of the ancient greek philosophers' venues?

The Academy was an olive grove owned by Plato, so it would be an example of an institution whose endowment was identical with its campus (and the modern equivalent would be a school in a penthouse, funded by the rents from apartments below and retail on the ground floor?)

The Lyceum https://en.wikipedia.org/wiki/Peripatetic_school#Background appears to have been a multi-use public park. Did Aristotle adopt the peripatetic lecture style because he enjoyed it, or did the Lyceum have intermittently patrolling Athenian rent-a-cops who encouraged his auditors to "move along now" every so often?

Stoics met in a stoa, so the modern equivalent might be a "strip mall philosopher."

Diogenes' tub might be a rude structure of cardboard under an overpass, or at best a cast-off camping tent. (as the SDFs in Paris have)