Grand Mosque, which is the greatest and the most famous of historical mosques in the city, is one of the first and oldest mosques in Anatolia. The structure was built on the area of Martoma Church, which was the biggest temple in the city center, in 639 at the era of His Holliness Omer. We are learning from the tablets that later in 1091 with the order of Great Seljuks Emperor Meliksah, the mosque had great reparation, and has got the shape it has today by having many reparations and additions in various eras. Seen in various places of the mosque, there are tablets belonging to, Great Seljuks Emperor Meliksah, İnal and Nisanoğuls, Anatolian Seljuks Emperor Gıyaseddin Keyhüsrev, Artuklus, Akkoyunlus emperor Tall Hasan and most of the Ottoman rulers. Diyarbakir Grand Mosque, referred to as a reflection of the famous Sam Emeviye Mosque, is considered to be 5th Harem-i Serif of Islamic world. In the faces of the yard of the Grand Mosque, decorations and inscriptionsbelonging to different eras are located in a great combination. Hıstorical Grand Mosque, which has been used as praying center through all eras of history, is the biggest structures complex in Diyarbakir. There are 2 mosques (Hanefis and Safiis parts), 2 madrasahs (Mesudiye and Zinciriye), east-west maksoorahs, minaret, privy and a great rectangular yard in the middle of all these complex structures. Entrance to the mosque is provided from three different places. The door to the east is the main (tac) door. There is a symetrically decorated figure which represents the challenge of lion and the bull at two sides of the main entrance door. The main door is about the challenge of two animals opens to yard in a pretty open arch way. The mosque was planned in a rectangular way and has many columns. Octagon planned fountain in the yard, is formed on eight columns. Sundial, which has a history of more than 800 years, is located inside the yard. The metal piece which is located on a meter up high circular marble shows the time with the shadow ability which turns around itself with the moves of the sun. Sundial, formed on a column with head, shows the time according to sun’s movements. It is known that the sundial, which was built by the famous scholar, who is known as the father of cybernetics, El-Cezeri, was located in the area outside the mosque but was then moved to its place where it is today in 1920s. In order to prevent it from ruining more a shelter made of iron was built around the partially cracked sundial, which is center of attraction of local and foreigner tourists coming to Diyarbakir.