Holy Wisdom, Turkish Ayasofya) is a former patriarchal basilica, later a mosque, now a museum, in Istanbul, Turkey. Famous in particular for its massive dome, it is considered the epitome of Byzantine architecture and one of the most beautiful buildings in the world. It was the largest cathedral in the world for nearly a thousand years, until the completion of the Medieval Seville Cathedral in 1520.

The current building was originally constructed as a church between 532 and 537 on the orders of the Byzantine Emperor Justinian, and was in fact the third Church of the Holy Wisdom to occupy the site (the previous two had both been destroyed by riots). It was designed by two architects, Isidore of Miletus and Anthemius of Tralles. The Church contained a large collection of holy relics and featured, among other things, a 50-foot (15 m) silver iconostasis. It was the patriarchal church of the Patriarch of Constantinople and the religious focus point of the Orthodox Byzantine Empire for nearly 1000 years.

In 1453, Constantinople was conquered by the Ottoman Turks and Sultan Mehmed II ordered the building to be converted into a mosque. The bells, altar, iconostasis, and sacrificial vessels were removed, and many of the mosaics were eventually plastered over. The Islamic features - such as the four minarets outside, the mihrab and minbar - were added over the course of its history under the Ottomans. It remained as a mosque until 1935, when it was converted into a museum by the secular Republic of Turkey.

The Blue Mosque was commissioned by Sultan Ahmet I when he was only 19 years old. It was built near the Hagia Sophia, over the site of the ancient hippodrome and Byzantine imperial palace (whose mosaics can be seen in the nearby Mosaic Museum). Construction work began in 1609 and took seven years.

The mosque was designed by architect Mehmet Aga, whose unfortunate predecessor was found wanting and executed. Sultan Ahmet was so anxious for his magnificent creation to be completed that he often assisted in the work. Sadly, he died just a year after the completion of his masterpiece, at the age of 27. He is buried outside the mosque with his wife and three sons.

The original mosque complex included a madrasa, a hospital, a han, a primary school, a market, an imaret and the tomb of the founder. Most of these buildings were torn down in the 19th century.

Inside, the high ceiling is lined with the 20,000 blue tiles that give the mosque its popular name. Fine examples of 16th-century Iznik design, the oldest tiles feature flowers, trees and abstract patterns. The overall effect is one of the most beautiful sights in Istanbul. The Iznik tiles can be seen in the galleries and and on the north wall above the main entrance. The remaining tiles, which have a less delicate design, were made in Kütahya.

The Basilica Cistern, located in the crowded Eminönü district of Istanbul next to the Hagia Sophia, was built to provide water for the city of Istanbul during the reign of Emperor Justinian I in the 6th century CE. This cistern is an underground chamber of 138 x 64.6 metres. The large space is broken up by a forest of 336 marble columns, which are aesthetically supported by strong columns and arches. The ceiling vaults, known as Manastır Tonozu (cloister vault), are built without using a mould. The cistern is surrounded by a firebrick wall with a thickness of 3.5 meters and is coated with a special mortar to make it waterproof.

Originally, there was a stone-paved circle on the cistern. It was later broken by dense housing construction beginning in the Byzantine period continuing into the Ottoman period. The citizens who settled in the vicinity were provided with their daily water requirements from the large round well-like holes opening from the ceiling structure. In 1940, several of the structures built on and around the Basilica Cistern were nationalized and a neat building was constructed at the entrance of the Cistern by the Istanbul Metropolitan Municipality. It was also exposed to a wide range of cleaning process between 1985-1988. Thus dirty water and tons of mud were removed and a promenade platform was built in the cistern. After the cleaning process was completed, the two Medusa heads, masterpieces of the First Age Art of Statuary were used as pedestals at the bottom of the two columns in the northwest corner of the cistern. It is not known exactly when or for what purpose the were antique Medusa and Gorgon heads were brought to the Basilica Cistern.

Topkapi Palace was not only the residence of the Ottoman sultans, but also the administrative and educational center of the state. Initially constructed between 1460 and 1478 by Sultan Mehmed II, the conqueror of Constantinople, and expanded upon and altered many times throughout its long history, the palace served as the home of the Ottoman sultans and their court until the middle of the 19th century. In the early 1850s, the palace became inadequate to the requirements of state ceremonies and protocol, and so the sultans moved to Dolmabahçe Palace, located on the Bosphorus. But despite this move, the royal treasure, the Holy Relics of the Prophet Muhammad, and the imperial archives continued to be preserved at Topkapi, and—since the palace was the ancestral residence of the Ottoman dynasty as well as the place where the Holy Relics were preserved— Topkapi continued to play host to certain state ceremonies. Following the abolishment of the Ottoman monarchy in 1922, Topkapi Palace was converted into a museum on 3 April 1924, on the order of Mustafa Kemal Atatürk.

Topkapi Palace, which developed and grew over the centuries, had a design that itself played an important role in Ottoman governmental philosophy and in the relations between the palace and its subjects. When Topkapi was first built, its plan was influenced by the splendor of the Edirne Palace located on the Tunca River, which had been constructed by Mehmed II’s father, Sultan Murad II (r. 1421–44, 1446–51) but very little of which survives today. The basic design of the palace is centered on various courtyards and gardens, around which are arranged offices devoted to state business, the buildings and pavilions serving as the residence of the sovereign, and the buildings set aside for the court employees who lived in the palace.

DISCOVERY ISTANBUL WITH ROMANTIC HOTEL