The ground level of Istanbul has risen anywhere from 15-40 feet since Roman times. Wars, fires, floods, earthquakes and 2,700 years of continuous inhabitation on this tiny peninsula have made Istanbul’s underground resemble a multi-layered cake. Only the baker won’t stop frosting it long enough for us to take a bite. Today, more than 30 blocks in Sultanahmet, including The Four Seasons Hotel, The Blue Mosque and a slew of carpet shops sit on top of the substructure of Constantine’s Great Palace. Students at Istanbul Erkek Lisesi sit in classrooms that conceal an ancient Greek Church and tunnels that are rumoured to connect to the famous Basilica cistern. In the neighbourhood of Balat, a massive Byzantine dungeon, where the most common form of torture was to burn out a prisoner’s eyes, is hidden by a peaceful Ottoman mosque and some private homes. The ancient walls near Harem have entranceways blocked off by iron gates. Many elder Istanbullus swear that as kids they explored these passageways and confirm the rumour of an extensive underground tunnel system snaking beneath the streets. They say these passageways connect palaces, churches, cisterns and many lead to the ruins of the Roman Hippodrome. That means there could be escape routes underneath the nearby hotel.