The Sultanahmet Mosque, better known as the Blue Mosque due to the prominent color of its majestic interior, is a historic mosque built in the early 17th century during the reign of Ahmed I. Among the city’s most famous landmarks, the Blue Mosque’s interior walls are adorned with over 20.000 hand-painted blue tiles, which are bathed in natural light filtering in from more than 200 windows – a dazzling sight to behold. Note that the Blue Mosque is still a functional mosque and visiting is forbidden during prayer times. The iron chain hanging over the central entrance to the courtyard was supposedly put in place to remind the sultan to lower his head in humility each time he entered the grounds on horseback.