Mesr is in the far east of Isfahan in Central part of Iran. It is basically 420 km far from Isfahan city, and 371 km from Yazd. Iran has a two main deserts, Lut and Kavir. Actually, Mesr is part of Kavir desert. Iranian Call Kavir, Dasht-e Kavir. Moreover, the central mountain ranges of Iran are close by. Interestingly, Mesr is the Farsi equivalent of Egypt. Why locals call this area Egypt is an amusing story that you can read here.