The building has been a hospital and a place to welcome the pilgrims until 1995, when it was transformed into the current Museum Complex. The name "della Scala" has been used since the 12th century and is due to its location in front of the steps of the Siena Cathedral.
It houses collections ranging from antiquity to modern times, in very different environments: from the Old Sacristy frescoed around the middle of 1400 by Lorenzo Vecchietta with the Articles of the Credo, to the Chapel of the Virgin so called for the eighteenth-century painting cycle that decorates it; the route then continues with the Church of Santissima Annunziata, with the Chapel of Relics frescoed by Domenico Beccafumi, up to the wonderful Sala del Pellegrinaio, built in 1320-1330 and characterized by a fifteenth-century painting cycle of great beauty and importance, created by Lorenzo Vecchietta and Domenico di Bartolo. This is the only pictorial testimony in Europe of the hospital life of that time, which shows a particular attention to details of clothing and architecture.
On the lower floor are the original marbles of the Fonte Gaia, the famous fountain in Piazza del Campo which was finished in 1419, but which unfortunately was damaged over the centuries; the one currently in the square is a copy, while here in the museum you can admire the fifteenth-century statues of Jacopo della Quercia representing Rea Silvia, Acca Larenzia and the Sapienza.
In the basements, since 1993, there is the National Archaeological Museum of Siena (collections of coins, seals and little bronzes) and the precious Treasure of Santa Maria della Scala consisting of a series of very important relics, some from Constantinople, among which stands out for example the Holy Nail of the Cross.