The most spectacular sights at Dainzú are the well-restored ball court and the Tumba del Jaguar (Tomb of the Jaguar), with the fearsome head of a jaguar perched above the door. Pre-Columbian pottery shards litter the ground all over, evidence that this is a site that, unlike Monte Albán or Mitla, is still in the earlier stages of excavation. You'll likely have it to yourself, too. The grass-covered ruins are particularly pretty in the late-afternoon light. Note that there are no facilities here. Keep an eye out for the turnoff, because it's poorly marked; arriving from Oaxaca City, it's right before an overpass.
Off Carretera 190, Dainzú, Oaxaca, 70430, Mexico