The most significant structure on the rather plain Plaza de los Trabajadores is this massive, 18th-century brick church, Camagüey's most distinguished and, in its day, the largest in Cuba. A chapel existed on this spot in 1601; the present structure dates to 1748 (it was reconstructed in 1848 and again in 1909 after a fire). The old convent still houses a rapidly decreasing number of nuns. The church is an eclectic architectural mix. Adorning the ceiling are surprising Art Nouveau murals, added in the 20th century. Also of note are the painted wood, neo-Gothic altar and the Santo Sepulcro, a 1762 casket elaborately fashioned from 25,000 silver coins and carried high by eight men during Easter processionals. Down narrow stairs behind the principal altar is a mysterious crypt, the remains of an extensive underground cemetery. Most of it was closed off after fire damage, but six macabre tombs with skeletons remain and are on creepy view alongside a small museum of 18th- and 19th-century objects uncovered at the church.