Death Valley is a valley in the state of California on Earth. Approximately 7,800 km² in size, it is noted for having the lowest elevation in North America at -86 meters below sea level, as well as extremely high temperatures.
Arriving at Sarek's house in early 2368 to discuss why Spock was on Romulus, Captain Jean-Luc Picard was greeted by Perrin, who compared the surface environment of Vulcan to Death Valley. (TNG novelization: Unification)
After hearing from Ezri Dax about Tobin Dax, Vic Fontaine commented that it sounded like Tobin would prefer to live in Death Valley than be around other people. (DS9 - The Lives of Dax short story: "Second Star to the Right...", "... and straight on 'til morning")