Isfahan is the capital of Isfahan Province. It is Iran's third largest city after Tehran and Mashhad. The city is located in the lush plain of the Zayandeh River, at the foothills of the Zagros mountain range. No geological obstacles exist within north of Isfahan, allowing cool northern winds to blow from this direction. Situated on the eastern side of the Zagros Mountains, Isfahan has an arid climate. Despite its altitude, Isfahan remains very hot during the summer. However, with low humidity and moderate temperatures at night, the climate can be very pleasant. During the winter, days are mild while nights can be very cold.