It was the most important gate into the city throughout the Middle Ages. Until the end of the 18th century it was also used as the Town Hall. Architects Francisco de Colonia and Juan de Vallejo began work on the principle façade (in the form of an altarpiece) in 1536. The Arch was completed in 1553 with the placing of the statues carved by sculptor Ochoa de Arteaga. They represent Carlos V, El Cid, Fernán González, Diego Porcelos, Nuño Rasura, Laín Calvo, the Guardian Angel and the Holy Virgin. Inside the Arch highlights include the Sala de Poridad, the immense mural of Count Fernán González (painted by Vela Zanetti in 1971) and the Pharmacy Museum. The Arch was re-opened in 1994 as an exhibition hall.