Ephesus features two main entrances, the "Upper" and "Lower" gates, located three kilometres apart. The site is packed with magnificent ancient structures, most notably: The Celsus Library: Dating back to the 2nd century AD, this iconic structure with its grand columns was one of the most important libraries of antiquity, alongside Alexandria and Pergamum. Monuments on Curetes Street: The Temple of Hadrian and the Hadrian Gate, both built in honour of Emperor Hadrian. Major Landmarks: The Artemision (Temple of Artemis), which is one of the Seven Wonders of the Ancient World; a massive Great Theatre with a seating capacity of 25,000; the Stadium; and the Commercial and State Agoras. Civic & Cultural Buildings: The Prytaneum (town hall housing the sacred fire of Hestia), an Odeon (a 1,800-capacity council chamber and concert hall), and the ancient harbour.