For more than 1,000 years, this complex across from the Duomo was home to Siena's hospital, but now it serves as a museum to display some terrific frescoes and other Sienese Renaissance treasures. Restored 15th-century frescoes in the Sala del Pellegrinaio (once the emergency room) tell the history of the hospital, which was created to give refuge to passing pilgrims and to those in need, and to distribute charity to the poor. Incorporated into the complex is the church of the Santissima Annunziata, with a celebrated Risen Christ by Vecchietta (also known as Lorenzo di Pietro, circa 1412–80). Down in the dark Cappella di Santa Caterina della Notte is where Saint Catherine went to pray at night. The subterranean archaeological museum contained within the ospedale (hospital) is worth seeing even if you're not particularly taken with Etruscan objects: the interior design is sheer brilliance—it's beautifully lighted, eerily quiet, and an oasis of cool on hot summer days.
The displays—including the bucchero (dark, reddish clay) ceramics, Roman coins, and tomb furnishings—are clearly marked and can serve as a good introduction to the history of regional excavations. Don't miss della Quercia's original sculpted reliefs from the Fonte Gaia. Although the fountain has been faithfully copied for the Campo, there's something incomparably beautiful about the real thing.