San Claudio is a Maya archaeological zone on the road from Tenosique toward El Ceibo and the Guatemalan border. The site reached its height around the Late Classic period and contains dozens of identified structures, including pyramids, platforms, a ball court, and an astronomical building.
It is more remote than Pomona and feels less visited. That makes it rewarding for archaeology-minded travellers, but also means you should arrange transport carefully and carry what you need for the outing.