Who was one of the landmarks that construted during the reign of Justinian was?

One of the landmark constructions during the reign of Emperor Justinian I was the Hagia Sophia in Constantinople (modern-day Istanbul). Completed in 537 AD, it was originally built as a cathedral and is renowned for its massive dome and stunning mosaics. The Hagia Sophia served as a central place of worship for the Eastern Orthodox Church for nearly 1,000 years and later became a mosque, reflecting the city's diverse religious history. Today, it stands as a museum and a symbol of Byzantine architecture.