The Desert National Wildlife Refuge Complex consists of four related areas within two hours of LV. The Moapa Valley NWR is not currently open to the public. You can see information about the other three below.

Hedgehog Cactus - Corn Creek Field Station
A dirt pull-off area on the south side of E. Lake Mead Blvd (NV 147) provides access to an overlook. The path is badly littered, the interpretative geology signs vandalized, and the smog makes for challenging photography, but maybe worth a stop if you're heading east early in the morning.

Las Vegas from Sunrise Mountain
The mouth of Grapevine Canyon, a dirt road drive from the highway and a short hike in, contains the densest petroglyth panels I have seen.

Petroglyths at Grapevine Canyon
Desert National Wildlife Refuge is located in the Mojave north of LV, with three 4WD access points off Highways 93 and 95. Visitors are on their own and should be well researched and equipped for the backcountry. This year's forays were scouting trips for future expeditions.

Recovering Yucca Forest - Mormon Well Road
Pahranagat National Wildlife Refuge is an oasis of lakes along Highway 93 about 80 miles north of LV. Birding, camping, and native rock art are its principal offerings, but it also contains a 4WD access into the Desert National Wildlife Refuge.

Upper Lake
The "Dunes" are more like badlands and the "Recreation Area" is a power toy playground.

Power Toy Tracks
Red Rock Canyon National Conservation Area is <1 hr. outside of Las Vegas. It features a scenic loop drive and hikes of various lengths and challenges.

View Coming Out of Icebox Canyon
Valley of Fire State Park is ~1 hr. outside of LV, with scenic drives and short hikes featuring unique scenery and native American petroglyphs. Popular Hollywood 'alien planet' landscape. Spectacular at sunrise/sunset.
2+ hours outside of LV, on the way to Death Valley, is the Ash Meadows National Wildlife Refuge. Springs fueled by the underground Amargosa River create oases and provide habitat for endangered species of desert pupfish. The lush vegetation and tropical-colored fish are a striking contrast to the surrounding alkaline uplands of the Mojave desert.

Hoover Dam is worth a look if you're in that part of Lake Mead NRA. But be warned: the tourist traffic is heavy, the post-911 tour is minimal, and the declining lake doesn't produce the dynamic flow shown on the official site.

The River (Not So) Wild