One of the most important tourist spots in Istanbul is Little Hagia Sophia, which is at only a few minutes’ walk from the great Blue Mosque. The building was originally built by the Emperor Justinian from the Byzantine era as the Church of Saints Sergius and Bacchus. The church was converted into a mosque in 1500. The building was part of UNESCO’s watch list of endangered monuments, and a lot of hard work has been put into restoring the place. You will see that the place has a new interior and exterior that has been done in Ottoman style and bears no resemblance to the usual Byzantine architecture and design. The restoration work was done carefully, and Hagia Sophia still has certain elements from the 1500s. The place has a unique floor plan that takes the shape of an octagon, and has several columns that have carved marbles. Visitors can pay a visit to the tomb of Huseyin Aga, who was the founder of the mosque. The mosque has a beautiful courtyard that contains a fountain in the centre, and also has several madrassas (religious schools), lodges for dervishes and has shops that sell books, ceramics, and Ottoman manuscripts.