Step 1: Rajasthan's western districts lie in the Thar Desert and are large in area but thinly populated. Step 2: Jaisalmer has an area of about 38,400 sq km, which makes it the largest district of Rajasthan and one of the largest in India. Step 3: Barmer, Bikaner and Jodhpur are also large, but each is smaller than Jaisalmer. Step 4: Dholpur is among the smallest by area. Remember: largest = Jaisalmer, most populous = Jaipur. Answer: Jaisalmer.