The northwestern portion of Rajasthan is generally sandy and dry. Most of this region is covered by the Thar Desert which extends into adjoining portions of Pakistan. The Aravalli Range does not intercept the moisture-giving southwest monsoon winds off the Arabian Sea, as it lies in a direction parallel to that of the coming monsoon winds, leaving the northwestern region in a rain shadow. The Thar Desert is thinly populated; the town of Jodhpur is the largest city in the desert and known as the gateway of the Thar desert. The desert has some major districts like Jodhpur, Jaisalmer, Barmer, Bikaner, and Nagour. This area is also important in the defence point of view. Jodhpur airbase is one of the largest airbases in India, BSF and Military bases are also situated here. A single civil airport is also situated in Jodhpur.