Istanbul Archaeological Museum Located in Old city (Sultanahmet)  Open 09:30-16:30 and Closed on Monday
This is in close vicinity of Topkapi Palace, in the direction of Gulhane park entrance. There are many collections in the museum. From Egyptian and Assyrian empires to Roman and Byzantine statues, marvellous sarchophagi, and pieces of Temples. The rich collection of ancient art are brought from anicent sites all over Anatolia (Turkey).

Istanbul Topkapi Palace Museum Located in Sultanahmet  Open 09:00-16:00 Closed Tuesday
Topkapi Palace is the symbol and the center of the Ottoman Empire. Overlooking Istanbul Bogazici (Bosphorus) and the Marmara sea, stands this amazing building that was the great palace of the Ottoman Sultans. The palace is a collection of buildings arranged around a series of courtyards and has incredible collections of jewels, China, pieces of Ottoman and Islamic artwork. 

Istanbul Chora Museum  (Kariye Museum) Fatih  Open 09:00-16:30 Closed Tuesday
Known also as St. Saviour, this church is famous for its mosaics. The second most importantByzantine church in Istanbul, has beautiful frescoes with the theme of death and resurrection.

Hagia Sophia Sultanahmet  Open 09:00-16:00 Closed Monday
Built by Constantin the Great, also known as the church of the Divine Wisdom designed to impress the strenght and wealth of the Roman emperors. Once it was the greatest Christian church in the world. 
Turkish and Islamical art museum Sultanahmet Open 09:00-18:30 Closed Monday Used to be the Palace of Ibrahim Pasa is a museum containing a large collection of Islamic artwork.
 
Basilica Cistern Istanbul Sultanahmet Open 09:00-17:30
Built in the fourth century, is one of the underground cisterns that riddle the foundations of the city. It has been extensively excavated and renovated and is worth visiting and exploring while listening to the tunes of classical music. A unique experience !

Dolmabahce Palace Besiktas 0212 258 5544 Open 09:00-16:00 Closed Monday & Tuesday
The Palace was built as a second residence to the Sultan Abdulmecid mid 19th century. The palace commands a nice view right on the Bosphorus and its gardens are very pretty, especially in spring and summer. The founder of Turkey, Mustafa Kemal Ataturk has died in this palace on November 10, 1938 at 9.05 AM. 

Military Museum Istanbul Harbiye 0212 233 2720 Open 09:00-17:00 Closed Monday & Tuesday
Display of ancient cannons,costumes, and weaponry from Ottoman Empires. Also the Janisary Band performs in front of the museums during the summer months, between the hours 15:00-16:00

The Ataturk Museum Sisli Closed Thursday and Sunday Tel: (212) 240 63 19
House where Ataturk lived and worked before the War of Independence during his stay in Istanbul between 1918 and 1919, originally was built in 1908 and restored by the Municipality of Istanbul in 1943, opening to the public in 1981. Top floor of this building was reserved to His mother Zubeyde Hanim and His sister Makbule, meanwhile Ataturk used middle floor for himself and lower floor for His loyal officer. On display are photographs of Ataturk from his birth until his death, as well as some of his clothes, personal belongings and paintings. It is located at Halaskargazi Street in Sisli district.

Asiyan Museum Bebek Istanbul Closed Sundays and mondays
This museum is the former residence of famous Turkish poet Tevfik Fikret (1867-1915) who constructed the building himself. In addition to an exhibit of the personal belongings of Fikret, there is a room devoted to the poet Nigar Hanim and displaying some of the belongings of Abdulhak Hamit.
It is located in Asiyan-Bebek district on the Bosphorus.

Calligraphy Museum Beyazit Istanbul Closed Sunday and Monday
The Beyazid Medresse, which was used as the municipality library since 1945 was evacuated, restored and reorganized as the Turkish Calligraphic Arts Museum. It has interesting and valuable examples of the Turkish art of the pen, Korans, imperial seals, diplomas, Hilye-i serif (descriptions of the Prophet), equipment and apparatus for calligraphic writing, samples of bookbinding, holy relics and miniatures, especially from Ottoman and Seljuk periods. Tel: (212) 527 58 51

Mosaic Museum Istanbul (The Great Palace Museum) Closed monday
The great palace museum is located to the south of the Blue Mosque inside the arasta which is the Kulliye of the mosque. The museum was constructed in order to include mosaic flooring that partially remained in good condition on the northeastern side of the Great palace of the Byzantine Empire. Tel: (212) 518 1205