It's the grandest of all the missions. It has a great history, try to leech on to a group where the ranger is discussing its history. That's what I did and I learned a lot. Like how many people lived there, what happened to them (the disease outbreak), how they made food, etc. They even have their own mill using water to make flour (which they still make for a company that donates the wheat for demonstrations). The whole thing blew my mind, it's gorgeous. I spent about an hour just walking around the grounds and looking at the architecture. Built in the late 1700's, it's a marvel it's still standing.
Make sure to go to all the missions, they aren't far from each other and it makes for a pretty cool couple of hours checking them out. Just make sure to talk to the rangers for cool facts you might not find out otherwise.
Also, please be respectful. I noticed some people leaving trash there and eating in the church. I know the tripadvisor community is a good honest group, but it disappoints me when I see people so blatantly disrespecting these priceless historical artifacts. *I'll get off my soap box, enjoy!
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.