Called the Blue Mosque by foreign visitors because of its interior tiles, it disappoints if you're looking for lots of blue because the blue tiles are mostly in the inaccessible upper galleries. Otherwise, the mosque is a fine example of Istanbul's wonderful imperial Ottoman mosques.
The Blue Mosque has fascinating secrets revealed on my Magic of the Blue Mosque page.
Because of the intense crowds, and the fact that the Sultan Ahmet is a working mosque, you must plan your visit carefully. It's closed to non-worshippers for 45 minutes before the call to prayer, 30 minutes afterwards, and all morning on Friday (until 14:30/2:30pm) , the Muslim holy day. Admission is free; donations gratefully accepted.
Here are the prayer times so you can plan your visit. By the way, the call to prayer from the minarets of the Sultanahmet Mosque is a phenomenon. With four of the finest müezzins in Turkey taking turns at the microphone, a seemingly nuclear-powered public address system feeding over 100 loudspeakers, the sound level exceeds 100+ decibels.
Splendid as the Sultan Ahmet I Mosque is, it's really no more splendid than several of the other great imperial mosques of Istanbul. If you can't stand crowds, you could substitute any of the other great imperial mosques and have a similar, but less hectic, less crowded and longer visit. More...
If you are a non-Muslim visitor, you must enter by the door on the south side of the mosque (to the right as you enter from the Hippodrome. If you're entering from the Ayasofya side, the tourist entrance is on the opposite side of the mosque.)
(Good thing the call is relatively short. Prolonged exposure to sound levels above 95 decibels may result in hearing loss.)
—by Tom Brosnahan