Mission San Carlos Borromeo de Carmelo, also known as the Carmel Mission, is a historic Roman Catholic mission church in Carmel-by-the-Sea, California. It is regarded as the most beautiful of all the California missions, and has been designated as a National Historic Landmark by the National Park Service. The mission is different from all others in the chain, in that the walls taper inward, forming a catenary arch, instead of the usual flat ceiling.