It was the last of the main squares to form. It is one of the most beautiful and preserved sites in the entire historic center of the Cuban capital. It was built between 1748 - 1832. Giving rise to the first public bath built in the City and where important families of the Havana aristocracy built beautiful mansions in its space that changed its swampy appearance. Over time it came to be called Plaza de la Catedral due to the naming of the church there as the Cathedral of the Archdiocese of Havana, a church with a baroque façade and asymmetrical towers, dedicated to the Immaculate Conception. Among its imposing colonial buildings are the house of the Marquis of Aguas Claras, currently being restored, the house of the Marquis of Arcos, former Artistic and Literary Lyceum, today the House of Poetry, and the Lombillo Palace, former post office and historian's office that Together with the house of Don Luis Chacón, today the Museum of Colonial Art, they constitute the museums of the square. The difference from other squares is the so-called Callejón del Chorro, where we find a commemorative tablet that marks the open gap that existed in one of its walls through which the Zanja Real, the first aqueduct the city had, drained.
Delimited by Mercaderes, Empedrado and San Ignacio streets.