To build a folly is essentially to do something a second time, something at an inopportune moment. That something is always the memory of something forgotten, about which we can paradoxically say "There it is again."
Follies were misunderstood, purposeless constructions. They were often only small, extravagant gestures in a garden, easily whisking off the imagination to distant lands, a sort of time capsule built to awaken the memory and induce surprise in passers-by. They marked locations, organized secondary paths in a park, or simply predicted the arrival of better times—a demarcation, a sacred spot, a mysterious trail, a hill whose tragic rocky nature begged for a tower, a party, or the arrival of summer.
“It is demonstrably true that things cannot be other than as they are. For, everything having been made for a purpose, everything is necessarily for the best purpose.” — Professor Pangloss
Tactical urbanism includes low-cost, temporary changes to the built environment, usually in cities, intended to improve local neighborhoods and city gathering places. Tactical urbanism is also commonly referred to as guerrilla urbanism, pop-up urbanism, city repair, or D.I.Y. urbanism.
The Street Plans Collaborative defines "tactical urbanism" as an approach to urban change that features the following five characteristics:
A deliberate, phased approach to instigating change;
The offering of local solutions for local planning challenges;
Short-term commitment and realistic expectations;
Low-risks, with a possibly high reward; and
The development of social capital between citizens and the building of organizational capacity between public-private institutions, non-profits, and their constituents.