Telescope Peak is the highest point in Death Valley at 3,380 meters. From here you can see both the highest point in the U.S., Mount Whitney, (Alaska excluded) and the lowest point, Badwater. The trail is about 22 km round trip with about 900 meters of ascent.
The trailhead begins at Mahogany Flat Campground, which is only accessible via a very bumpy backcountry road. Four wheel drive and high clearance is highly recommended.