The entire complex is one of the areas of the Holy See regulated by the 1929 Lateran Treaty signed with the Kingdom of Italy.

In the courtyard of the palace is the well where, according to tradition, Pope Callixtus I was martyred in the year 222.

[2] The palace was originally the residence of the titular cardinals of the Basilica of Santa Maria in Trastevere and was renovated in the 16th century under Cardinal Giovanni Morone by architect Orazio Torriani.

[3] In 1936 during the pontificate of Pope Pius XI the architect Giuseppe Momo, known for the double helix staircase of the Vatican Museums, designed the construction of a new wing.

[2] One facade of the palace faces the celebrated Fountain in Piazza Santa Maria in Trastevere.