Historic in architectural form, this museum and event space is housed in a 178-year-old mansion–turned–boarding house that once sat atop the city’s earliest sewer system. When Jorge Eckstein, an Argentine chemical engineer of Hungarian parents, bought the ruined building in 1985, the trash and rubble piled to the ceiling of the first floor. Discovering the forgotten tunnels—and inside them implements that told a multicentury history—Eckstein restored the mansion and its catacomb-like basement. Displays run from an old underground slave cell to photos from the area’s 19th-century heyday, and tell the city’s story in a way no book could. This visit offers a wonderful—and bizarre—view into the city’s past, not to mention into the owner’s obsession with revealing it.