The 198,000-acre Red Rock Canyon National Conservation Area (just west of Summerlin and Blue Diamond) is the place for mountain biking and rock climbing and is relatively close to the heart of Las Vegas.
Amongst the red sandstone peaks and along the Keystone Thrust Fault (look for the red line running across the mountains) you will find miles and miles of single-track winding through the canyon.
While finding your way through the trails, keep your eyes peeled for the diverse wildlife that can be founds through out the Mojave. According to the Red Rock Canyon Interpretive Association, there are 1,750-2,000 plant species (the area is shrub-dominated desert), 45 mammal species form carnivores to insectivores and 100 bird species seasonally.
Make sure you stay on the designated tracks - though the desert looks rough and tough, the ecosystem is delicate.
Sport Climbing is popular in the Calico Hills and Sandstone Quarry areas of Red Rock Canyon. Trad Climbing area include Brass Wall, Necromancer Wall and Eagle Wall.
There are a few way to get to Red Rock Canyon. For explicit directions, check out this link.
Be sure to check the Las Vegas Gov website for information about the Canyon before you go – and a stop by the visitor center to get more information is a good idea as well.