Site of a basilica and palace from early Roman imperial times, as well as an military installation built by Septimius Severus for the Roman imperial cavalry bodyguard. Now the site of the Archbasilica of St. John Lateran (rebuilt in the 16th century): Complesso dei San Giovanni in Laterano (Basilica, Palazzo Apostolico Lateranense, edifici annessi) Holy See; listed as a UNESCO World Heritage Site in 1990.