A massive red-sandstone fort located on the banks of River Yamuna was built under the commission of Emperor Akbar in 1565 and was further built by his grandson Shah Jahan. The fort, semi circular on plan, is surrounded by a 21.4 m high fortification wall. The fort was built primarily as a military structure; parts of it are still reserved under Indian Army. Later on, it was transformed it into a palace, it also became a gilded prison for eight years after his son Aurangzeb seized power in 1658. The fort houses a maze of buildings, including vast underground sections. The Amar Singh Gate to the south is the sole entry point. A path leads straight from here up to the large Moti Masjid. Just before this is the open Diwan-e-Aam, where Shah Jahan listened to people’s petitions or issues. A small staircase just to the left of Diwan-e-Aam throne leads up to a large courtyard. To the left is a beautiful white marble Nagina Masjid.Nagina Masjid is a beautiful mosque located in Agra Fort. It is located near Moti Masjid. This mosque is constructed with pure white marble and has a beautifully designed prayer chamber. The Mosque built in the north-western corner of the Machchi Bhawan was meant for the personal use of the Emperor. It has a marble paved court enclosed by walls to the north, south and east and the prayer chamber on the west. The prayer chamber is also made up of marble and has three domes on its top. The mosque has a three-arched façade with the cusps and supported on slender piers as its entrance. The arch in the middle is larger and has nine cusps and ones on the either sides have seven cusps only.Other places to see within the Fort are Diwan-e-Khas - which once housed Shah Jahan’s legendary Peacock throne and the diamond Koh-I-Noor, Shish Mahal- a palace with walls inlaid with tiny mirrors, and Khas Mahal - the white octagonal tower and palace. In the South of the fort, there is a huge red-sandstone Jahangir’s Palace, built by Akbar probably for his son Jahangir.