Once the location of the town's vegetable market, Piazza delle Erbe is Mantua's most lively piazza. Its 13th-century Palazzo della Ragione sports a 15th-century clock tower at its south end that marks the phases of the moon and signs of the zodiac.
Mantua's oldest church, the 11th-century Rotonda di San Lorenzo, sits just below street level alongside Palazzo della Ragione.