The roads accessing Chaco Canyon, home to Chaco Culture National Historical Park, do a fine job of deterring exploration: they are mostly unpaved and can be very muddy and/or icy during inclement weather (particularly NM 57 from the south). The silver lining is that the roads leading in—and the lack of gas stations, food concessions, or hotels once you get off the highway—keep this archaeological treasure free from the overcrowding that can mar other national park visits: only about 85,000 people visit annually, compared with at least 10 times that number to Canyon de Chelly, which is 80 mi away as the crow flies.
Once past the rough roads you'll see one of the most amazingly well-preserved and fascinating ruin sites on the continent. The excavations here have uncovered what was once the administrative and economic core of a vast community—the locus of a system of over 400 mi of ancient roads that have been identified to date. While there is evidence that people lived
in the canyon at least since 400 AD, the majority of these roads, and the buildings and dwellings that make up the canyon site, were constructed from 850 to 1250 AD. Several of the ancient structures—such as an immense Great Kiva, Casa Rinconada, or Pueblo Bonito—are simply astounding, if only for the extreme subtlety and detail of their precisely cut and chinked sandstone masonry. But there's still a shroud of mystery surrounding them. Did 5,000 people really once live here, as some archaeologists believe? Or was Chaco maintained solely as a ceremonial and trade center? The more that's learned about the prehistoric roadways and the outlying sites that they connect, or wondrous creations such as the Sun Dagger —an arrangement of stone slabs positioned to allow a spear of sunlight to pass through and bisect a pair of spiral petroglyphs precisely at each summer solstice—the more questions arise about the sophistication of the people that created them.
At the visitor center you can meander through a small museum on Chaco culture, peruse the bookstore, buy bottled water (but no food), and inquire about hiking permits. From here you can drive (or bike) along the 9-mi paved inner loop road to the various trailheads for the ruins; at each you can find a small box containing a detailed self-guided tour brochure (a 50¢ donation per map is requested). Many of the 13 ruins at Chaco require a significant hike, but a few of the most impressive are just a couple of hundred yards off the road. The stargazing here is spectacular: there is a small observatory and numerous telescopes, which are brought out for star parties from April through October; ask about the schedule at the front desk. Pueblo Bonito is the largest and most dramatic of the Chaco Canyon ruins, a massive semicircular "great house" that once stood four stories in places and held some 600 rooms (and 40 kivas). The park trail runs alongside its fine outer mortar-and-sandstone walls, up a hill that allows a great view over the entire canyon, and then right through the ruin and several rooms. It's the most substantial of the structures—the ritualistic and cultural center of a Chacoan culture that may once have comprised some 150 settlements.