The citadel of Van (Tushpa) was the main settlement of the Urartian kingdom, which dominated the regions of eastern Anatolia, Caucasia and northwestern Iran between the ninth and sixth centuries BC. Lake Van borders the site on the west, while to the south is the eastern extension of the Taurus mountains, stretching east to west and reaching 3000-3500m in height. These steep mountains, rising like a natural wall between the Urartian city and its greatest enemy the Assyrian kingdom to the south, provided an advantageous defensive feature. The capital city Tushpa, which is 1.5km east of Lake Van, and the Van plain itself are bordered on the east by the 3200m high Erek mountain. Erek mountain surrounds the east of the plain like a crescent, halting the cold winds as well as providing the water supply for agriculture in the Van plain from its rich water sources. Although the soil of the Van plain, which is 1750m above sea level, is agriculturally fertile, for many crops it is barely possible to conduct successful agriculture without irrigation. The Van plain, 9km wide and 17km long, is poor in water resources, as is well known. The water sources around Erek mountain, amongst the richest in the east Anatolian region, were used effectively in the period of the Urartian kingdom for the first time. Almost all the irrigation structures built on and around Erek mountain were built in order to irrigate the Van plain to the east of Lake Van. Most of the constructed dams and reservoirs, totalling more than ten, are still in use today, with minor restoration, despite being more than 2,700 years old. If we consider that few irrigation facilities were constructed at other water sources in the east Anatolian region, it underlines the importance of these water sources at Erek mountain and its slopes for the plain of Van. It seems that the rich water sources around Erek mountain constituted another positive condition for the foundation of the capital city of the Urartian kingdom in the Van plain.