If it is sunny, you'll catch a few young people and older gentlemen sitting at the base of a statue in the middle of the open space. The statue is a brooding, hooded Giordano Bruno—an excommunicated Dominican monk and one of the earliest cosmologists who held the idea of an infinite universe. He was burnt at the stake for heresy on this spot on 17 February 1600. The piazza is used as a marketplace during the day, and party central for college students and tourists at night. When the sky gets dark and the street lamps go on, the Campo de' Fiori fills with people and lovers wander arm in arm in the crowd. Over the buzzing of conversation and the occasional burst of laughter you may hear a young vocalist belt out O Sole Mio at the top of his lungs as change plunks into his accordion case.