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 City of Jodhpur is the largest city in the desert and a major metropolitan area of India which is known as the gateway of the Thar desert. The desert has some major districts like Jodhpur, Jaisalmer, Barmer, Bikaner, and Nagaur. This area is also important from a defence point of view. Jodhpur airbase is one of the largest airbases in India, BSF and Military bases are also situated here. Currently four civil airports are located here: Jodhpur, Jaisalmer, Bikaner and Nagaur, of which Jodhpur is the major civil airport, being the 44th busiest airport in India and one of the oldest air strips of India, being built in the 1920s. The Northwestern thorn scrub forests lie in a band around the Thar Desert, between the desert and the Aravallis. This region receives less than 400 mm of rain annually. Temperatures can sometimes exceed 45 °C in the summer months and drop below freezing point in the winter. The Godwar, Marwar, and Shekhawati regions lie in the thorn scrub forest zone, along with the city of Jodhpur. The Luni River and its tributaries are the major river system of Godwar and Marwar regions, draining the western slopes of the Aravallis and emptying southwest into the great Rann of Kutch wetland in neighbouring Gujarat. This river is saline in the lower reaches and remains potable only up to Balotara in Barmer district. The Ghaggar River, which originates in Haryana, is an intermittent stream that disappears into the sands of the Thar Desert in the northern corner of the state and is seen as a remnant of the primitive Sarasvati river. Flora and fauna The Desert National Park in Jaisalmer is spread over an area of , is an excellent example of the ecosystem of the Thar Desert and its diverse fauna. Seashells and massive fossilised tree trunks in this park record the geological history of the desert. The region is a haven for migratory and resident birds of the desert. One can see many eagles, harriers, falcons, buzzards, kestrels and vultures. Short-toed snake eagles (Circaetus gallicus), tawny eagles (Aquila rapax), spotted