Yazd, also called YEZD, city, central Iran. The city dates from the 5th century AD and was described as the "noble city of Yazd" by Marco Polo. It stands on a mostly barren, sand-ridden plain about 4,000 feet (1,200 m) above sea level. The climate is completely desertic. A network of qanats (tunnels dug to carry water) links Yazd with the edge of the nearby mountain Shir Kuh (mountain). Historically, Yazd has been the link between Fars and Khorasan. It was situated at the intersection of the trade routes from central Asia and India. It served as a provincial capital and earned the title of Dar al-ibada (Home of Piety), owing to its many religious buildings. Some of the city's inhabitants are Zoroastrians whose ancestors had fled toward Yazd and Kerman when the Muslim Arabs conquered Iran. Yazd is now the most important centre of Zoroastrianism in Iran. Since Sassanian times Yazd has been famous for beautiful silk textiles that were rivaled in later periods only by those of Kashan and Esfahan. The city is still a major centre of silk weaving. It has spinning and weaving mills, a plant for the manufacture of water purification and filtration equipment, and considerable mining and quarrying activity; copper deposits nearby are processed at the Sar Cheshmeh facilities. Almonds, fruit, and some grain are grown near the city. Besides a few remains of the imposing medieval city wall, the city has many important mosques and mausoleums. The Masjed-e Jom'eh (Friday Mosque) is distinguished by the highest minarets in Iran, mosaic faience (earthenware ceramics), a superb mihrab (pulpit) dated 1375, and two oratories that are Gothic in appearance. Some of the other mosques and mausoleums in the city are decorated with delicate and rich stucco relief or are polychromed with tones of pale blue, rose, and yellow. The skyline is picturesque with minarets and many tall towers that were designed to bring cool air from underground into the buildings' chambers. Yazd city is linked with Kerman, Qom, Esfahan, and Tehran by road and railway; it also has an airport. The economy of the area in which Yazd is situated is dominated by agriculture that was modernized through the establishment of farm corporations and processing centers for agricultural products.