Founded in 1797 to bring Christianity to the local indians, the Mission of Saint John the Baptist is among the prettiest of all California's missions. The buildings have been damaged by earthquake on more than one occasion but repairs and restorations over the years have left the mission looking as beautiful as ever. Famously, the mission and grounds featured prominently in Hitchcock's "Vertigo", but the bell tower scenes were actually shot on a studio set.
If you go:
Take a walk past the cemetery and you will find a short section of El Camino Real, the highway that connected all the California missions.
Links:

Old Mission San Juan Bautista
406 Second Street
San Juan Bautista, California 95045 USA
Mailing address:
P.O. Box 400,
San Juan Bautista, CA 95045-0400 USA
Phone Numbers:
Information
+1 (831) 623-2127
+1 (831) 623-2127