The Sultan Ahmet or Blue Mosque (in a region now called Sultanahmet) was constructed for Sultan Ahmet I between 1609 and 1616. The sultan died a year after its completion, 27 years old. This mosque is probably the one most tourists will remember, because this is where most tours and guides will take them. I think there are better mosques in town, and in particular don’t like the crowds. But the building has some good spots and I try to show them in a good light. The ground plan is more square than the other mosques that were inspired by the Haghi Sophia. Most designs would have two semidomes to the east and west of the central dome. Here, however, domes to the north and south side have been added. The Strolling through Istanbul authors were not much impressed by the effect, and neither am I. Though I do recall sitting in the huge space in the early 70’s when I first visited it and being taking by the enormous space. I would often come in the early evening and be alone. You should try that nowadays. To illustrate the latter point I added pictures taken during a June 2009 visit, showing the mosque but also the fair-like activities at its fringe. In 2018 during a december visit I found the number of visitors had grown so large that I decided to not visit. A string of visitors was led along three sides of the courtyard, then on into the garden, to enter at one side of the mosque. At another side a similar, continuous, string left the building. Only days before I had been al alone in the (much better) Selimiye in Edirne. I did visit Ahmet's mausoleum though.
From a viewer: This mosque is one of the three holiest Islamic places in Istanbul (The other two are the Sultan Eyüp complex, with the grave of prophet Mohamed’s companion and standard bearer Abu Ayyub al-Ansari, and the Chambers of the Holy Relics of Islam in the Topkapı Palace, where the Mantle of the prophet and many other for muslims venerable objects are kept). Namely, it was from this mosque’s courtyard that in Ottoman times, after a solemn prayer, the yearly pelgrimage caravan towards Mecca took of, loaded with the presents the Sultan had selected that year and accompanied by a crowd of pilgrims from Istanbul and the Balkans. In the same context, it is notable that a piece of stone from the Kaaba has been inserted into the mihrab of the Sultan Ahmed mosque.