St John's (Sv. Jāņa baznīca) is one of the oldest churches in Riga, built by Dominican friars in the 13th century and later given to the city as a Lutheran church. The building is a striking mix of Gothic and Renaissance elements added at different periods.
The interior is spacious and relatively unornamented in the Lutheran tradition, but worth a look for its carved altarpiece and the unusual arches of the nave. The courtyard (Jāņa sēta) alongside the church is a quiet space in the middle of the Old Town, with fragments of the original city wall visible.