Towering buttes, jagged pinnacles, and rippled sand dunes make this an otherworldly landscape. Changing colors and shifting shadows during the day add to the enchantment. Most of the natural monuments are remnants of sandstone eroded by wind and water.
Agathla Peak and some lesser summits are roots of ancient volcanoes, whose dark rock contrasts with the pale yellow sandstone of the other formations. The valley lies at an elevation of 5,564 feet in the Upper Sonoran Life Zone; annual rainfall averages about 8.5 inches.
In 1863-1864, when Kit Carson was ravaging Canyon de Chelly in Arizona to round up the Navajo, Chief Hoskinini led his people to the safety and freedom of Monument Valley. Merrick Butte and Mitchell Mesa commemorate two miners who discovered rich silver deposits on their first trip to the valley in 1880. On their second trip both were killed, reportedly shot by Paiutes.
Hollywood movies made the splendor of Monument Valley known to the outside world. Stagecoach, filmed here in 1938 and directed by John Ford, became the first in a series of Westerns that has continued to the present. John Wayne and many other movie greats rode across these sands.
The Navajo have preserved the valley as a tribal park with a scenic drive, visitor center, and campground. From Mexican Hat [1], drive 22 miles southwest on U.S. 163 and turn left and go 3.5 miles to the visitor center. From Kayenta, go 24 miles north on U.S. 163 and turn right and go 3.5 miles. At the junction of U.S. 163 is a village-worth of outdoor market stalls and a modern complex of enclosed shops, where you can stop to buy Navajo art and crafts.
At the entrance to the Monument Valley Navajo Tribal Park find a visitor center (435/727-5874, 6 a.m.-8 p.m. daily May-Sept., 8 a.m.-5 p.m. daily Oct.-Apr., $5 per person, $2 ages 60 and over, free for children six and under) with exhibits and crafts. This is a good place to get a list of Navajo tour guides to lead you on driving or hiking trips into the monument. Lots of folks along the road will also offer these services.
Take one of several guided tours leaving daily year-round from the visitor center to visit sites such as a hogan, a cliff dwelling, and petroglyphs in areas beyond the self-guided drive. The trips last 1.5-4 hours and cost $45-90 per person. Guided horseback rides from near the visitor center cost around $75 for two hours; longer day and overnight trips can be arranged too. If you'd like to hike in Monument Valley, you must hire a guide; hiking tours of two hours to a day or more can be arranged at the visitor center.
A 17-mile, self-guided scenic drive (6 a.m.-8:30 p.m. May-Sept., 8 a.m.-4:30 p.m. Oct.-Apr.) begins at the visitor center and loops through the heart of the valley. Overlooks provide sweeping views from different vantage points. The dirt road is normally okay for cautiously driven cars. Avoid stopping or you may get stuck in the loose sand that sometimes blows across the road. Allow 90 minutes for the drive. No hiking or driving is allowed off the signed route. Water and restrooms are available only at the visitor center.
Don't be surprised to find that lodgings at Monument Valley are expensive; they're also very popular, so be sure to book them well ahead.
The Navajo-owned 
View Hotel (435/727-5555, www.monumentvalleyview.com [2], $195 and up) provides the only lodging in the Monument Valley Tribal Park. Views are terrific from this stylish newer hotel; reserve a room well in advance.
Goulding's Lodge and Trading Post (435/727-3231, www.gouldings.com [3], $130 and up) is another great place to stay in the Monument Valley area. Harry Goulding and his wife, Mike, opened this dramatically located trading post in 1924. It's a large complex tucked under the rimrocks two miles west of the U.S. 163 Monument Valley turnoff, just north of the Arizona-Utah border. Modern motel rooms offer incredible views of Monument Valley. Guests can use a small indoor pool; meals are available in the dining room. A gift shop sells a wide range of souvenirs, books, and Native American crafts. The nearby store has groceries and gas pumps, a restaurant is open daily for all meals, and tours and horseback rides are available. The lodge stays open year-round, and rates drop in winter and early spring. Goulding's Museum, in the old trading post building, displays prehistoric and modern artifacts, movie photos, and memorabilia of the Goulding family. The campground at Gouldings ($25 without hookups, $42 with hookups) is pleasant and well managed.
About a half an hour south in Kayenta, Arizona, the adobe-style Hampton Inn (on U.S. 160, 520/697-3170 or 800/426-7866, $149 and up) is the nicest place in town, and it's only a little more expensive than its Kayenta neighbors.
Links:
[1] http://www.moon.com/destinations/utah/canyonlands/utah-s-southeastern-corner/mexican-hat
[2] http://www.monumentvalleyview.com
[3] http://www.gouldings.com