Southwest of Tucson, the vast desert homeland of the Tohono O’odham Indians stretches out, a hot wasteland where few dare to venture. You can reach this 4,400-square-mile borderland reservation via Highway 286 west of Tucson, but there isn’t much out there except gorgeous, mostly untouched desert. Straddling the border, the reservation is a popular, albeit deadly, corridor for illegal immigrants heading north, and dozens die crossing the reservation every year — only the O’odham know how to live out here.

About 90 minutes west of Tucson along Highways 86 and 386 (follow the signs), you’ll find Kitt Peak National Observatory (520/318-8726, www.noao.edu, daily 9 a.m.–3:45 p.m., $2 suggested donation), operating 23 telescopes — the world’s largest collection — atop the 6,875-foot peak in the reservation’s Quinlan Mountains. Docent-led tours are available at 10 a.m., 11:30 a.m., and 1:30 p.m. and last about an hour ($4 adult, $2.50 child 6–12), or you can pick up a pamphlet and take a self-guided tour.

The visitors center has exhibits on astronomy and a gift shop selling star- and planet-related items and O’odham baskets. Far off to the west look for 7,700-foot Baboquivari Peak, the home of I’itoi, the tribe’s sacred “elder brother” god.

The reservation capital, Sells, is a small outpost about 58 miles southwest of Tucson on Highway 86. There’s a supermarket, a few businesses, offices, and a school. During the first weekend in February O’odham cowboys join in the All Indian Rodeo and Fair, during which locals set up food booths, play music, march in a parade, dance, and show off and sell their crafts.

Continue through the thick desert west on Highway 86 and you’ll hit Ajo, a copper mining community with a few restaurants and a good place to see the scars that strip mining leaves open on the land.

South of Ajo on Highway 85, past the tiny town of Why, you’ll find Organ Pipe Cactus National Monument. This rugged, beautiful monument along the border protects what amounts to pretty much all of the Organ Pipe cacti in North America, along with many other species of cactus, and is a popular area for seeing spring wildflowers in bloom. It has in the past been named one of the most dangerous national monuments in the country, as the area is a major drug-smuggling corridor, but it is safe to visit. Just make sure to lock your car and don’t stray off the well-traveled park roads.

The Kris Eggle Visitor Center (520/387-6849), named for a ranger who was killed during a shootout with drug smugglers, is open daily 8 a.m.–5 p.m. A campground with 208 sites has drinking water but no hookups or facilities ($12 per night). The 21-mile Ajo Mountain Drive, on a twisty dirt road that’s usually passable, will take you into the monument’s center, where you can see the goofy, many-armed cacti up close.