Known in its time as the Queen of the Missions, it's certainly the largest and arguably the most beautiful of all on the Mission Trail. Because it's a little more remote and pastoral, surrounded by thick stone walls, you can really get a sense of what life was like here in the 18th and 19th centuries. It's also the location of the main visitor center.
Ranger-led tours cover life in the mission and show up close the magnificent church and its famous rose window, a stunningly carved masterpiece attached to the sacristy. The best time to visit would absolutely be on Sundays at 12:30pm, when they hold a mariachi Mass.