A brooding example of Baroque style, the palace houses part of the 16th- and 17th-century sections of the collection of the Galleria Nazionale d'Arte Antica and is across the road from the Villa Farnesina. Among the most famous paintings in this large, dark collection are Guido Reni's Beatrice Cenci and Caravaggio's St. John the Baptist. Stop in, if only to climb the 17th-century stone staircase, itself a drama of architectural shadows and sculptural voids.
Behind, but separate from, the palazzo is the Orto Botanico (Mon.–Sat. 9:30–6:30 in summer, 4:30 in winter; €8), Rome's only botanical park, containing 3,500 species of plants. There are various greenhouses around a recently restored stairway/fountain with 11 jets. Or, if you prefer, it's just a peaceful park where kids can run and play.