What is "elagabalium"

The Elagabalium was a temple built by the Roman emperor Elagabalus, located on the north-east corner of the Palatine Hill. During Elagabalus' reign from 218 until 222, the Elagabalium was the center of a controversial religious cult, dedicated to Deus Sol Invictus, of which the emperor himself was the high priest.