Valadier’s original simple facade was added to with a majestic pronaos, porticoed on the ground floor, open in a loggia on the first floor, and crowned by a triangular pediment.
The lower section of the forepart has a base made of smooth ashlars that imitate travertine, and forms a covered atrium that allowed carriages to pass through.

Today it is home to the bookshop.

Base moderna con frammento di sarcofago antico
Second half of 3rd century AD
Base moderna composta da un'ara antica
End of the Flavian era (end of 1rst century BC - early years of the second century AD)