A short walk south of the Campo dei Miracoli, behind an unmarked door on Via Luca Ghini, lies the world's first university botanical garden, founded in 1544. The current layout — a series of compartments planted by botanical family, with greenhouses, a herb garden, and a small palm court — dates from the 18th and 19th centuries. Mature magnolias, ginkgos, and a cork oak planted in 1805 give the place a feeling of accumulated time.
Almost no tourists find it, which is part of why it works. Bring a book, sit on a bench under the wisteria, and watch the resident cats stalk the gravel paths. The small Museum of Botany on the grounds, in the former Sala delle Botaniche, holds Renaissance herbaria and antique scientific instruments. Allow an hour, more if it is sunny.