According to Kate Torgovnick’s recent TED Blog post, they are: Venice, Amsterdam, Marrakech, Antigua, and Quebec City.
Extrañamente, San Miguel deserved this honorable mention as one of the most walkable cities not for its cobble-stoned streets but for the triumph of its residential topology of courthouse architecture and the “hidden worlds” which lie behind the centro’s thick adobe walls. “Trespassers delight,” is Torgovnick call.
Thus, the new trend of urban exploration arrives in San Miguel, where the most enthused pedestrian visitors are now likely to dive into any open door they see and wander around a patio. Fear not, they’re largely harmless, the urbexer’s creedo’s quite simple, “Take nothing but pictures, leave nothing but footsteps, break nothing but the silence.”
Also, accompanying the article, is an interesting talk “The Walkable City” by Jeff Speck, where the urban planner discusses the numerous benefits of adopting the downtown pedestrian lifestyle.
To sum up: Whether or not trespassing as an urban explorer is an idea worth spreading, being on foot in a highly walkable city is a good thing.