The Valens Aqueduct, also known as Bozdoğan Kemeri, is one of Istanbul’s most important Roman-era structures. Completed in 378 AD by Emperor Valens, it was part of a 250-kilometer water system supplying Constantinople’s cisterns and public fountains. Originally built to address the city’s chronic water shortage, it was later connected to major reservoirs like Yerebatan and Binbirdirek Cisterns during the reign of Justinian I. The aqueduct suffered damage during the Avar Siege of 626, and later Ottoman sultans, including Mehmed II and Süleyman the Magnificent, restored and expanded it. Standing 29 meters high and spanning 971 meters, it remains a dominant feature of Istanbul’s skyline. Once supplying the Topkapı Palace, today it stands as a testament to the city’s 1,500-year water heritage, bridging antiquity with modern Istanbul.