Concierge.com's insider take:

Though currently surrounded by ranch-house subdivisions, the Carmel Mission was once the only building for miles around. Spanish missionary Father Junípero Serra established the mission in 1771 to convert Native Americans to Christianity. Today, it's still an important site for Catholics—primarily because Father Serra's remains are interred under the altar—but even nonbelievers will find it worth a visit. The primitive statuary and ornately carved altar are beautifully preserved, as are unexpected details like the charming cherubs peeping from behind the pipes of the organ loft. Adjoining the church are the living quarters of the missionaries. One of the most interesting rooms is the tiny library (California's first), where you can peer through a glass doorway at decaying leather-bound texts frozen in time. Outside in the courtyard, baseball-size roses grow in the lovely gardens. (Shutterbugs: One of the best spots to pose for pictures is behind the Basilica, beneath the bell tower.)

California's missions were positioned one day apart by horseback, so you can see several in a day traveling by car. If you're heading south on Highway 1, it's easy to make a detour to Mission San Antonio de Padua, in the middle of nowhere near the tiny town of Jolon (Mission Rd.; 831-385-4478). It provides a glimpse of how the missions looked before modern-day civilization grew up around them.