The Royal Presidio Chapel, also known as San Carlos Cathedral, was constructed in the 1790s in current-day Monterey, CA. It is the oldest building in Monterey and the only remaining original chapel of the four Spanish Presidios that once existed in California. It is the longest continuously active church in California, established on June 3, 1770 when Father Junípero Serra said the first Mass under what became known as the Vizcaíno-Serra Oak..

The first chapel was constructed of wood in 1770 and replaced by an adobe building that was later destroyed by fire. The present adobe chapel was constructed from 1791-1795. The chapel was designed in Mexico City at the Academy of San Carlos. The main facade of the chapel is embellished with pilasters, decorative niches, and sculptures.