4 Piazza Orazio Giustiniani
Repurposed Roman slaughterhouseDuring the late 19th and most of the 20th centuries, the Testaccio district hummed with activity from the sprawling slaughterhouse. Thought animal slaughter was moved away from Testaccio in 1975, most of the building has been preserved. In recent decades, areas have been slowly transformed for new functions. The place houses a contemporary art exhibition space called the MACRO, a university campus, and even an organic supermarket (open Tuesday to Sunday).