St. Jacob's (Jekaba baznica) 
Klostera 2, tel. (+371) 732 64 19. Open 07:00 - 20:00. Closed Sat. 
This church beside the parliament was first mentioned in the chronicles in 1225. In 1522, it became the first church in Latvia to hold a Lutheran service, but during a brief Polish occupation 60 years later it was returned to its Catholic flock, who have held it ever since. This year it's celebrating its 775th anniversary. (Sun 10:00 - English)