Chaco Culture National Historical Park is well worth the trip over rough roads, and they now offer reservations for the campground.
It's a UNESCO World Heritage site (other such sites are the Pyramids in Egypt, Taj Mahal in India, etc.) and has some of America's most important pre-Columbian structures.
The rangers offer free walking tours by day and Night Sky programs at the Observatory. If you like stars, Chaco is far away from lighted population centers.
Aztec Ruins National Monument or Salmon Ruins were outliers, part of the Chacoan world linked by roads, and can give you a taste of what Chaco offers if you are short on time or don't want to take the RV on the road to Chaco.
