Sultanahmet Camii (The Blue Mosque),
Sultanamet Old City of Istanbul

The Blue Mosque (Called Sultanahmet Camii in Turkish) is an historical mosque in Istanbul. The mosque is known as the Blue Mosque because of blue tiles surrounding the walls of the interior. The Mosque was built between 1609 and 1616 during the rule of Ahmed I and just like many other mosques, it also comprises a tomb of the founder, a madrasa and a hospice. Although still used as a mosque, the Sultan Ahmed Mosque has also become a popular tourist attraction in Istanbul but it's closed to non worshippers for a half hour or so during the five daily prayers.
The best way to see the great architecture of the Blue Mosque is to approach it from the Hippodrome (west side of the mosque) as if you are a non-Muslim visitor using same gate to enter the Mosque.

Source: http://www.bluemosque.co/