The important Huastec ceremonial center of Tamtoc flourished from AD 700 to 1500. Today it’s one of the few maintained Huastec sites. The cleared part of the expansive site is a plaza with platforms made of river stones. Look for a low bench with two conical altars decorated with faded 1000-year-old frescoes believed to represent Quetzalcóatl, the feathered serpent god. It's not the most overwhelming of sites and probably of interest mainly to specialists.
It's 49km from Ciudad Valles, and you'll need to take a taxi or have your own transportation to get here.