The Blue Mosque is a historic mosque located in Istanbul, Turkey. It is officially known as the Sultan Ahmed Mosque after the Ottoman sultan commissioned its construction in the early 17th century. 

The Blue Mosque is one of the most famous landmarks in Istanbul and is a popular tourist attraction. It is known for its stunning architectural features and beautiful blue-tiled interior, which gives the mosque its popular name.

The Blue Mosque is an important example of Ottoman architecture and is known for its six minarets (tall, thin towers) and sizeable central dome. The mosque's exterior is adorned with intricate carvings and decorations, including calligraphy, geometric patterns, and glazed tiles. 

The mosque's interior is covered with blue tiles, giving it a distinctive appearance. The tiles were made using a unique glazing technique called faience, developed during the Ottoman period. The Blue Mosque also has a large central prayer hall with a capacity for over 10,000 worshippers.

The Blue Mosque is an active place of worship and is open to visitors, although there are certain times when it is closed to tourists to accommodate prayers. It is an important religious site for the city's Muslim population and is a popular place for tourists in Istanbul.