This is the mosque that most visitors see first. In many cases it's the only mosque that they see. Built on the orders of Sultan Ahmet 1 and still bearing his name, the Blue Mosque of Sultanahmet dominates, in conjunction with Aya Sofya, the Hippodrome area which has always been the center of the city. Mehmet Aga was the architect and the Mosque took 7 years to build. The Sultan himself joined the builders on several occasions to lend a hand but died within 12 months of its completion at the age of 27.
It is difficult, and probably pointless, to attempt to avoid comparison with Haghia Sophia and certainly futile to say which is the most impressive structure. I have my own opinions and you will arrive at yours I'm sure. One key difference is that the Blue Mosque is a living place of worship and carries out this function continually. As a visitor you will be ushered in through a side gate and your access to the Mosque is carefully controlled. If you're going to be spending any time in Turkey and want to see Ottoman or Selcuk art then you're going to have to get used to visiting mosques. It's really not very scary. If you dress appropriately you'll feel more comfortable, but if you don't you will be provided with something to hide behind. A word of caution, in the winter the mosque is very, very cold so you'll want to wrap up warm (several pairs of socks is probably a good idea). Due to the status of the building as a functioning mosque there's not much of the building that you're free to explore. The interior is very impressive though many commentators feel that the elephantine columns lend a heaviness which detracts from the overall feel. Highlights include the fine Iznik tile work on the lower parts of the walls, the carving and inlay work of the doors and windows and the carved stone of the mihrab and mimber.
Istanbul certainly has finer and more delicate examples of Islamic devotional architecture but there is something to be said for the scale of the Sultan Ahmet Camii. Don't forget to take in the buildings surrounding the mosque itself and forming the kulliye, the foundation built at the same time as the mosque and comprising a primary school, medrese (seminary), hospital, public kitchen, karavansaray and market. Not all of these buildings survive but those that do give an idea of the scale

THE BLUE MOSQUE

THE BLUE MOSQUE
The Sultanahmet Mosque (The Blue Mosque) is one of the most impressive monuments in the world; it is the cachet which makes our city -Turkish-. When one looks from the Galata Bridge and the Golden Horn, the magnificent Suleymaniye Mosque of the architect Sinan seems as dominating on the skyline. However, when entering Istanbul Harbour from the sea, one is struck by the majesty of the Blue Mosque with its tall slender minarets and half and full domes atop one another causing the building to rise in gracious curves. Observed next St. Sophia which is massive and thick, the Blue Mosque caresses the eye like a beautiful flower or a princely gem cut by a master craftsman. On entering the Mosque, by lifting the curtain at the door, every one, whatever his national or religious origin, is struck with the blue mist seeming to fall from the colored windows and faiences, the coolness reaching the soul.The Mosque of Sultan Ahmet and its dependent building were built in the years 1609-1619. The Mosque is surrounded on three sides by a wide courtyard which may be entered by any of five doors. The front is surrounded by twenty-six granite pillars with marble stalactite heads, supporting thirty domes. In the middle of this marble paved front yard sits a hexagon-shaped columned Sadirvan (washing fountain): its effect is striking. The front yard has three entrances; the main door, in the west, possesses a noble style. The Mosque has itself three doors. The one entering from the courtyard is the largest and is still in use today.The interior of the Mosque is a huge rectangle with a length of 51,65m and a width of 53.40m. The diameter of the main dome is 22.40 m. and it stands 43 meters high at its central point. The dome rests on four semi-arches and four pendentives; all of these arches correspond to four semi-domes. The corners carry four domes of smaller size, there are galleries resting on pillars. All of the walls are hooped. Two fountains have been built at the foot of the two pillars at the entrance. On three sides of the interior there are galleries resting on pillars. All of the walls are covered with marvellous faiences of blue and green reaching up as far as the upper windows. The Sultanahmet Mosque derives its worldly-known name of "The Blue Mosque" from the luminous quality of these faiences. It is surprisingly bright inside the Mosque due to the light pouring in through two hundred and sixty windows; but unfortunately these windows do not contain the original stained glass any longer. Up until the late 18th century however, the rugs and faiences of the Mosque appeared even more lustrous under the mystic lights of the original windows.
The architect of the Mosque was Mehmet Aga, known as «Sedefkar», (worker of mother-of-pearl). We read the life story of Mehmet Aga from a hand-written book called the «Brochure of Engineering» written by a contemporary of his, Cafer Celebi. According to this book which is at present in the Topkapi Palace Library, he had started his career as a gardener at the Mausoleum of Sultan Suleyman. Later he was appointed to the Palace garden and there he started working on mother-of-pearl in which he excelled from the very beginning. In addition to this, he was a talented musician and had mastered mathematics and geometry. Mehmet Aga entered the Corps of Janissaries in 1562. After a succession of increasingly important duties he was appointed to the Water Administration. After being promoted from this position, Mehmet Aga built many mosques, fountains, and other edifices. He repaired the Kaaba and became one of the outstanding architects in the world.According to the famous «Seyyahatname» of the great Turkish traveller, Evliya Celebi, a suitable place for the Blue Mosque has been sought for a long time. The southern part of the Byzantine Hippodrome was selected as the best area due to its proximity to the Palace and its large flat surfaced area. This area was also right next to its competitor St. Sophia and over looked the sea. The Sultan paid thirty thousand talents of gold dinars from his own treasury to the owner of the property, Ayse Sultan, who herself was related to the Dynasty.The time chosen for laying the cornerstones was a sunny but cold day in January, 1609. The head architect Mehmet Aga had determined the positions of the main pillars, niche, and courtyard after measuring the site with a ruler in one hand and an amber rosary in the other. All the state officials were gathered together. A platform had been built at a prominent place for the Sultan and his throne placed on it. The young Sultan Ahmet I had come from the Palace with a sable-skin falling from his shoulders. The Sheikhulislam, high officals of the Moslem Judiciary, the Grand Vizier, viziers, and governors all had helped in laying the first foundations. Finally, the Sultan had approached the foundations wearing the magnificent headgear (kavuk) with tiara representing the foot of Mohammed. His sable-skin coat's skirt was filled with stones and earth. As the sun sparkled from his diamond encrusted «kavuk» he had poured the stone-earth mixture into the foundation, dedicating it with his famous words: «O, Allah! It is the service of Ahmed, your believer, accept it!»During the years of construction after this ceremony, the young Sultan Ahmet, who was very anxious to see the Mosque completed, visited the site every Friday and aided the workers in their tasks. His ideal was to make the Blue Mosque greater than St. Sophia which stood nearby as a constant reminder of the magnitude of the undertaking.The Mosque when completed in 1616 was a work of grandeur. Twenty one thousand forty three pieces of valuable porcelain wares, each costing eighteen «akce» covered the walls. The carved marble of the pulpit was a great work of art. Silk carpets graced the floors and hundreds of crystal chandeliers dangled from above. The Sultan had ordered the jewelled chandeliers in his treasury to be placed in the Mosque. Inside the lower window niches were placed hundreds of Korans ornamented with gold and other water colors. One thousand one hundred and eighty one talents of gold and two thousand nine hundred and forty four «akce» were spent from the Sultans treasury for the construction of the Mosque. In addition to this the janissaries and the cavalry soldiers had worked without any wages: white one group was working the other rested, and the following day they changed places. Even the state officials had presented many gifts for the furnishing of the Mosque. The Sultan also built several pious foundations around the Mosque such as hospitals, schools and guesthouses, through the passing years, however, most of them have been closed because of fires and financial reasons.During its lifetime, the Mosque has seen many rebellions interrupt its silent and mystical life. In fact, Sultan Mahmut II, one of the outstanding rulers in the Ottoman history, proclaimed the decree abolishing the Corps of janissaries in the Blue Mosque in 1826. Today this mosque of Sultanahmet rests as a tribute to the great past of the Turkish nation.