With some walls dating back to 1738-50, and undergoing a major renovation that transformed the Spanish colonial church into a Gothic Revival cathedral in 1868. It’s an interesting church; not particularly huge, and with strangely truncated and out of proportion bell towers, it nonetheless anchors one of the two major plazas of the colonial core.
Update: From the vault, added in October 2018:
The 18th century portion of the cathedral, more or less intact, now serves as the apse/presbytery (area around the altar). The gothic revival portion of 1868 was built onto the front of the 18th c. structure, with the original facade removed.
Interesting, thank you!