On a weekend in early March, a mass of alt-tourists descended on New Orleans, walking from an anarchist bookstore to a fancy art gala to a crawfish boil to one of the city's cemeteries to help pick up trash, and on and on for 24 hours straight.This was all part of 24Hrs, an ongoing series of free-form pedestrian excursions in cities around the country, conceived by an urban studies group called the Psychogeography Project. The events, which have also taken place in New York and Philadelphia, are devoted to "critical, spontaneous, performative exploration of urban space." The goal is to uncover and document aspects of cities that gentrification and rebuilding threaten to destroy.Calvin Johnson, a co-founder of the project and a leader of the New Orleans trip, says the marathon nature of the events helps promote a feeling of disorientation and discovery. "There's a sense at about five a.m. or six a.m. where basically your defense mechanisms break down," he says. "By the end, it feels like an acid trip without the acid."