The Cathedral of St John the Baptist anchors the north side of the Plaza 23 de Marzo. Built in the early 20th century and remodelled several times since the major 1950s earthquake, it is a simple, twin-towered church in white-painted stucco — modest by Chilean cathedral standards but the visual heart of central Calama.
The interior is plain, with a wooden roof and a few stained-glass windows. Most visits last ten minutes; the building is more useful as an orientation point and a brief stop on a walk around the plaza than as a destination in its own right.