The Blue Mosque (or as it is known as Sultan Ahmed Mosque) was built by Sultan Ahmed I in the period between 1609-1616 AD, in order to confirm the Ottoman authority. This impressive mosque features an array of layered domes, surrounded by six minarets adorning the city skyline. The mosque is the largest and most visited of the Ottoman mosques. Despite its popular appeal, entry to it is seriously controlled because the mosque is still used for religious purposes, so tourists are not allowed to enter during prayer times.