This monumental is representative of the urban structures in ancient Baiae: a road with several taverns and a private villa. The name Protiro translates as "colonnaded doorway" and comes from the villa's particular little entrance porch which was framed by two long stone benches.

The Villa has a series of rooms with a central atrium to provide them with light. Within these rooms there are some wonderful mosaics, particularly that to the northeastern which is a combination of black and white marble tiles laid in a most distinctive pattern.

To the south of the atrium a vast room opens up with an apse of which the semicircle remains span a width of 10.37 meters. This was probably unrelated to the initial plan but is richly decorated in large marble slabs resplendant of the late-imperial domus ostiensis.