The Marble Arch, also Arch of the Philaeni (Italian: Arco dei Fileni), formerly known in Libya as El Gaus (i.e. "The Arch"), was a monument in Libya built during the days of Italian colonization. The arch marked the border between Tripolitania and Cyrenaica, and was located on the actual Libyan Coastal Highway (at that time Via Balbia) near Ra's Lanuf. It was designed by architect Florestano Di Fausto in response to a request by the Italian Governor-General Italo Balbo. It was unveiled on 16 March 1937 in a lavish night ceremony attended by Benito Mussolini.
The arch, which was 31 meters high, with an opening 15.75 meters (51 feet 8 inches) high and 6.5 meters (21 feet 4 inches) wide, and made with travertine stone (Rome's typical building material), was located some 30 km (19 mi) west of the possible borders between Carthage and Cyrene, the locality called in Antiquity Altars of the Philaeni (Latin: Arae Philaenorum) which was located approximately halfway between Ra's Lanuf and El Agheila.
The landmark was named after the legendary Philaeni brothers of Carthage, who chose to be buried alive on that spot in order to gain this border for their home town. It bore two giant bronze statues of the brothers, represented as buried alive, surmounted by a stylised altar, mocking one of the disappeared Arae. The landmark was decorated by basreliefs which illustrated the legend.