St John the Baptist is the oldest surviving church in Cardiff's city centre, a Grade I listed building that has stood on the same spot since the 12th century. The current structure is largely 15th century, with a notably tall tower that serves as a landmark visible from the arcades. It is one of the few medieval buildings in the centre that survived Cardiff's Victorian redevelopment largely intact.
The church is open to visitors and free to enter. Inside, the Herbert Chapel contains some of the finest Elizabethan funerary monuments in Wales, including effigies of members of the Herbert family who once owned Cardiff Castle. The building is small enough to absorb in 20 minutes but gives a useful sense of what Cardiff looked like before the coal boom remade the city.