Believed to be the regional capital of the Zoque during the Classic period, these ruins were inhabited between AD 250 and AD 400. The site's most prominent characteristics are its use of megalithic granite architecture, and its most impressive structure, the namesake 'Old Church,' is a 95m by 65m pyramid utilizing stone blocks weighing over a ton each. Instead of steps, the apex is reached via a ramp – look for the petroglyph cross at the south side of its base.
The other distinctive feature here is the presence of many carved anthropomorphic and zoomorphic monuments scattered throughout the site. The most well-known are the Sapodrilo (it appears to be a cross between a toad and a crocodile) and the Altar de las Cuatras Caras (Altar of the Four Faces).
Few people make the really quite minimal effort required to visit, which gives the ruins a haunting, deserted quality. From the signed turnoff at Km 10 on the Tonalá–Arriaga highway, it's about 9km (30 minutes) east off the main road; a high-clearance vehicle is required mid-May through November because the last 2km up can be washed out, but walking a section may still be required. There is no public transportation.
An exuberant authority on regional archaeological sites, the distinguished Ricardo López Vassallo lives in Tonalá and can organize transportation.