The gate sits at the terminus of an old road once leading to the town of Alcala. It was built according to the design by Francisco Sabatini during 1774-1778. It replaced an earlier gate made of bare stone, which the king didn't consider elegant enough to serve as an entrance to the capital city of the country. The result was a spectacular construction in the style of a classical Roman triumphal arch.

The gate stands a proud 20 metres. It's made of granite , and its arches are built out of the excellent limestone from Colmenar. It's very elaborately decorated on both sides; the central arch is adorned in a different way at the front and at the back. The part facing the visitor arriving in the city features 10 Ionic columns, the part turned inwards – pilasters. Each part is topped with a stone with an engraving commemorating the king who commissioned the gate: 'Rege Carolo III, Anno MDCCLXXVIII.'