The Arch of Caracalla is a triumphal arch. It was built in 217 AD by Marcus Aurelieus Sebastenus, governor of the Roman province called Mauretania Tingitana. The Arch of Caracalla was built in honor of the Roman Emperor Marcus Aurelius Antoninus, nicknamed Caracalla, and his mother, Julia Domna. It celebrates Caracalla's grant of Roman citizenship to the freemen of the province. Like all Roman triumphal arches, it is made of marble. The Arch of Caracalla has two huge columns, known as piers, and single archway in the center. A bronze statue of Caracalla in a six-horse chariot once topped the monument. While the Arch of Caracalla sits at one end of a ceremonial street, Decumanus Maximus, it is neither a city gate nor part of a rampart. The triumphal arch is a free-standing monument.