At the Basilica Cistern, visitors step into an impressive underground space built in the 6th century by the Byzantine Emperor Justinian I. The cistern, which once stored water for the Great Palace of Constantinople, features 336 marble columns and a peaceful, cool atmosphere. One of the highlights is the Medusa head columns—two ancient stone carvings of Medusa, one placed upside down and the other sideways. These add a mysterious touch to the site. As you explore, you’ll also learn about the cistern’s history and its importance in Istanbul’s water system. The Basilica Cistern is a unique and fascinating place to visit for anyone interested in history, architecture, or just looking for a special experience. For guided tours: Please meet your guide at Dsign Cafe at least 15 minutes before the tour time. For easy recognition, look for the white flag with the Istanbul Tourist Pass® and logos.