Beyazıt Square sits on the grandest public forum old Constantinople ever built — and pieces of it still lie loose at its edges. In 393 the emperor Theodosius I dedicated a vast ceremonial plaza here, entered through a triumphal arch whose columns bore a strange carved teardrop pattern. Earthquakes and stone-robbers buried the rest, but the arch's fat column drums still lie at the square's western rim, unlabelled and easy to walk past. Around them the Ottomans raised their own landmarks: the Bayezid II Mosque, the city's oldest imperial mosque still standing in its original form, and the grand gate of what is now Istanbul University.
Today the square is one of Istanbul's great crossroads. You step out of the Grand Bazaar's western gate into sudden open sky, pigeons lifting in clouds, the smell of simit and roasted chestnuts. Students stream under the ornate arch, old men sell bird seed by the handful, and the fire-watch tower rises behind the campus wall. Stand still a moment and watch the crossing: the plaza is doing the job Theodosius gave it sixteen centuries ago — a place the whole city passes through.