Topkapı Palace, one of the most famous landmarks of Istanbul that once housed Ottoman sultans while the city was the capital of the empire, is undergoing one of the most comprehensive restorations in its history. The project that costs about TL 220 million ($56.4 million), is part of the gradual restoration work at the palace in the last decade. In order to not harm the delicate stone structure at the heart of the city, workers use tiny hammers instead of sledgehammers, officials assure.

The palace was built in 1478 upon the orders of Mehmed II also known as Fatih (Conqueror) for his conquest of the city from the Byzantine Empire, 25 years before the construction of the palace. It served as the main palace of the Ottoman Empire for 540 years before sultans switched to other sites in Istanbul in the final days of the empire.

Authorities say the ambitious project is the biggest restoration work in the palace's history and hope that it will resume its former glory.

Topkapı currently serves as a museum which attracts tourists from around the world with its collections of Ottoman artifacts.

Some 500 workers, restorers and art experts work in 18 different sections of the sprawling complex overlooking the Marmara Sea. The work covers an area of 340,000 square meters. Ayşe Erdoğdu, director of the museum, told Ihlas News Agency that they work to make the palace more functional and make more sections "visible" to visitors. "The original palace covered an area of 700,000 square meters. More than a decade ago, some old structures, which were part of the palace, were included within the boundaries of the palace museum," she said.

One section that will be opened to the public will be military warehouses that date back to the rule of Sultan Abdülaziz, who reigned between 1861 and 1876. Erdoğdu said the collections in Fatih kiosk will be back on display after the restoration while the Seferli Ward of the palace will host the clothes of sultans. Parts of the palace's kitchens were opened to the public but a larger area will be available for visitors by the end of the year. Erdoğdu said they also completed the restoration of a library. "We also work on reinforcing the structures and the infrastructure," Erdoğdu says. Authorities have confirmed earlier reports that a pavilion in the palace was under the risk of collapse due to cracks on the walls. The damage forced the closure of the building where the treasury of the Ottoman Empire was once located. Though the exact cause remains unknown, it is believed that earthquakes throughout the centuries, including a major tremor in 1999, may have caused the cracks in the historical building.

Selman Ünlügedik, head of the Istanbul authority in charge of the preservation of historic buildings, said although this slowed down the resoration process, the palace is still open to visitors. He said they paid the utmost attention to preserve the palace in its original texture. "We use what Ottomans use to build the place, from stones to iron components. This is not an ordinary place and we have to be very careful. The most useful tool we have is not a sledgehammer but a tiny hammer weighing only 250 grams," he said.