Sessorium, Palace and archaeological site in Esquiliae district, Rome, Italy

The Sessorium was an imperial palace complex in Rome featuring thermal baths, an amphitheater, and extended gardens near the Claudius Aqueduct. The site contained multiple structures added and modified across different periods.

Septimius Severus began the palace in the Horti Variani and Elagabalus completed it; the Historia Augusta places the order to kill Alexander Severus here in late 221. Between 271 and 275 the Aurelian Wall absorbed most of the complex, turning the Amphitheatrum Castrense into a bastion. In the early 4th century Helena, mother of Constantine, used part of it as her residence.

The great 36-by-22-metre hall of the palace was turned into a Christian basilica in the mid-4th century, a conversion the Liber Pontificalis attributes to Constantine himself. Tradition holds that relics Helena brought back from Jerusalem were kept in a chapel there. Restored under Pope Benedict XIV in the 18th century, the basilica became Santa Croce in Gerusalemme and absorbed the whole complex.

The remains are located on the grounds of Viale Castrense 5 in Rome and accessible by public transportation. The site is walkable, though some areas may have limited access and sturdy footwear is advisable.

The Circus Varianus was cut by the Aurelian Wall, which ran through its seating tiers, so only about 20% of the racecourse lay inside the city. The Amphitheatrum Castrense was walled up and turned into a bastion of the same circuit.