St. Louis the King Cathedral, San Luis Potosí, Cathedral in San Luis Potosí, Mexico.

St. Louis the King Cathedral has a pink cantera stone facade built as a screen, with six salomonic columns on each of its first two tiers and niches holding twelve Carrara marble apostles carved by the Biaggi brothers. The south tower dates from 1730; the north tower, a copy in grey stone, was added in 1910. Inside, three naves with eight vaults in the central one lead to a two-tier cypress altar with Louis IX of France and Our Lady of the O.

A 1592 adobe parish with a tejamanil roof first stood here; it was demolished and replaced from 1670 by a lime-and-stone church built under master Nicolás Sánchez, funded by gold and silver from Cerro de San Pedro, and finished in 1730. It was consecrated as a cathedral in August 1854 under Pius IX, and in 1896 Bishop Ignacio Montes de Oca y Obregón had the interior fully decorated.

The cathedral is dedicated to Nuestra Señora de la O (Our Lady of the Expectation), a Marian devotion celebrated on 18 December, when the image kept in the main altarpiece is honoured. The Carrara marble apostles on the facade, carved by the Biaggi brothers for Bishop Montes de Oca, replaced earlier stone figures and copy those inside Rome's Archbasilica of St John Lateran.

The cathedral faces the Plaza de Armas, with its main door on the plaza side and the nave running back to Calle Morelos. The south tower dates from 1730 and the north tower from 1910, so the two differ in stone colour. The carillon in the north tower is played from a keyboard and can also be controlled electronically from the Netherlands.

The facade holds twelve Carrara marble apostles carved by the Biaggi brothers for Bishop Montes de Oca, copies of those inside Rome's Archbasilica of St John Lateran. Twelve more quarry-stone apostles line the roof edges, giving the cathedral 24 apostle figures, a count the sources call unmatched by any other church.