5 Impressive Byzantine Monuments to See in Istanbul

1. Hagia Sophia
Hagia Sophia, also known as “the Great Church,” was once the cathedral of Constantinople and is located at the heart of the First Hill, near the Great Palace and Hippodrome. A true masterpiece of Byzantine architecture, Hagia Sophia is celebrated for its magnificent interior, featuring stunning mosaics and towering marble columns. Emperor Justinian I famously declared, “Solomon, I have outdone thee!” in reference to its lavish design. The current structure, built in the sixth century, is the third church on this site—replacing earlier versions destroyed by fires during riots.

After centuries as a museum, Hagia Sophia was converted into a mosque in 2020 and is now officially known as the Hagia Sophia Grand Mosque (Ayasofya-i Kebir Cami-i Şerifi). Its groundbreaking architecture, rich history, and immense religious significance make it one of the most iconic buildings in the world. The church’s breathtaking domes, which seem to float in mid-air, its monolithic marble columns, and its unparalleled mosaics place it among the wonders of global architecture. Remarkably, it was constructed in just 5 years, 10 months, and 24 days, with materials brought from Syria, Egypt, Greece, and Asia Minor. Upon its grand opening in 537, Emperor Justinian declared, “Thank God for giving me the chance to build such a church.”

The most famous feature of Hagia Sophia is its massive dome, which sits at the center of the church, flanked by two half domes. These half domes together match the diameter of the central dome, which measures 31.24 meters (102 feet 6 inches) in diameter and rises to 55.6 meters (182 feet 5 inches) in height. Though it has undergone several repairs, the dome remains an architectural marvel.

Visiting Hours: Open daily from 09:00 AM to 7:30 PM (2026).

2. Basilica Cistern (Bazilika Sarnıcı / Yerebatan Sarayı)
The Basilica Cistern, constructed between 527 and 565 AD under Emperor Justinian I, is one of the most impressive ancient water reservoirs in Istanbul. Built after the Nika Riots of 532 AD, it is a testament to Byzantine engineering and architecture.

The cistern was essential for water management in ancient Constantinople, especially during the dry summer months. Though over 200 cisterns existed in the city, this one was the largest and most important. It earned the nickname “Basilica Palace” because of its marble columns, which rise from the water. The cistern spans 140 meters in length and 70 meters in width, covering an area of 9,800 square meters and holding up to 100,000 tons of water. Inside, it features 336 columns, many repurposed from older structures, with some carved from single pieces of marble.

Two Medusa heads, serving as column bases, are among the cistern’s most famous features, their strange orientations (one upside down, the other on its side) adding to its mystique.

Visiting Hours: Open daily from 9:00 AM to 11:00 PM.

3. Hagia Irene Church (Hagia Eirene)
Hagia Irene is one of the earliest and most significant Byzantine churches, built on the site of a pre-Christian temple. It holds the distinction of being the first church completed in Constantinople, predating Hagia Sophia by a few years. The church is located in the outer courtyard of Topkapı Palace.

Hagia Irene, named after a young Persian noblewoman, is the oldest Byzantine church in the Eastern Roman Empire and the second-largest in Istanbul after Hagia Sophia. The church features a 16-meter-diameter dome and is primarily constructed from thin red bricks and mortar. Although much of its original decoration was altered during the Iconoclastic period, the church still retains some of its early Byzantine features.

It has served various roles over the centuries, including as an Ottoman arsenal and later as a concert hall in the Turkish Republic era. Unlike many other churches in Istanbul, it was never converted into a mosque, preserving its original form.

Visiting Hours: Open daily from 9:00 AM to 6:00 PM, except on Tuesdays.

4. Aqueduct of Valens (Bozdoğan Su Kemeri)
Completed by Emperor Flavius Julius Valens in 378 AD, the Aqueduct of Valens (Bozdoğan Su Kemeri) is an extraordinary feat of Roman engineering. Located in the Saraçhane area of Istanbul, it was part of a vast water transport system that brought water to Constantinople for centuries, filling the city’s numerous cisterns and pools.

The aqueduct originally began near the Church of the Holy Apostles and ended at the Forum of Theodosius. Today, the surviving section stretches 971 meters in length and reaches a height of 28 meters. It consists of 86 arches, with many sections made of brick added during later Byzantine restorations. The aqueduct channeled water over the valley between the city’s Third and Fourth Hills, supplying a cistern built by Emperor Theodosius I near Beyazit Square.

Restored several times throughout history, the aqueduct underwent repairs by Emperor Justin II and later by Constantine V after it was damaged by the Avars in 626. After the Ottoman conquest in 1453, the aqueduct system was further restored and expanded by Sultan Mehmed II and other sultans.

5. Chora Church / Khora (Kariye Camii)
The Chora Church, also known as Kariye Camii, is famous for its breathtaking mosaics and frescoes, which are among the finest examples of late Byzantine art. Located outside the city walls, the name “Khora,” meaning “rural area” in Greek, reflects its location beyond ancient Constantinople’s limits. These mosaics and frescoes are celebrated for their depth and dynamic figures, precursors to Renaissance art.

Built in the early 4th century as part of a monastery complex, the church was rebuilt during the reign of Emperor Justinian I in the 6th century. In the 13th century, Theodoros Metokhites oversaw extensive restoration work, adding new frescoes, mosaics, and a library. He also created a “History of the Prophets” mosaic presentation in Chora to teach religious history.

Chora’s realistic, three-dimensional frescoes and mosaics stand out from other Byzantine structures and were visible to visitors during the Ottoman period, even though they were covered during prayer times. This helped preserve them to this day.

Check our Istanbul tours for visiting the Byzantine monuments.

Visiting Hours: Open daily from 9:00 AM to 6:00 PM, except Fridays.