The Great Guest House was built around the end of the XIth. Century, when the demand for monastic hospitality was such that a proper hospice detached from the monastery was needed. During the medieval period the Great Guest House was therefore the centre of hospitality for pilgrims and guests.
The current Guest House is largely a reconstruction dating from the late nineteenth and early twentieth century, during which the building was crowned with battlements. However, a significant mistake was made in that these battlement are stylistically Ghibelline (dovetail), whereas the abbey should have had battlements in the Guelph style (simple parallel pipes), reflecting its tie to the papacy.
The Little Guest House probably originated as some sort of service centre, though the exact use is difficult to identify. Today the Great Guest House is used as conference room, while the Little Guest House has become the ticket office and bookshop.