The palace that the Emperor Tiberius had let build had a rectangular shape,
with a façade on the Forum and another on the Velabro. Caligula, his successor, added as well some
constructions on the side towards the Forum, which were named “Palace of Caligula”.
Among all the palaces built on the Palatine, the Domus Tiberiana was the first
really important building; One could count 18 rooms on the south side of the Palace.
A huge underground gallery (cryptoporticus) decorated with paintings and paved
with mosaic was used to link the palaces between each other.
Palace of Caligula.
A closer view of the palaces, left the Palace of Caligula and in the centre of the picture, the Palace of Tiberius.