Basilica Cistern (Yerebatan Sarnıcı), Istanbul (must see)

Deep beneath the busy streets near Hagia Sophia lies one of Istanbul’s coolest secrets — literally — the Basilica Cistern. Its Turkish name, translating to something like “the cistern that sank into the ground,” sounds dramatic… and honestly, it lives up to the hype. Built in the 6th century AD by Emperor Justinian I, this underground wonder once helped supply water to the Great Palace of Constantinople. And yes, history tells us, more than 7,000 slaves worked on it, which in turn explains how it became so massive.

The endless rows of columns, dim lighting, and still water reflecting everything like a spooky mirror... If this feels a bit like stepping into a fantasy movie set, that’s because thousands of years ago, the Byzantines were already masters of atmospheric design. Even when the Ottomans took over, the cistern kept doing its job quietly — providing water to Topkapi Palace and proving itself far more reliable than your average plumbing system.

These days, the Basilica Cistern is less about water supply and more about blowing visitors’ minds. You can stroll past ancient triumphal arches, admire rows of marble pillars, and, of course, meet the most famous residents: two giant Medusa heads casually holding up columns in the northwest corner. One sideways, one upside-down… because when you have mythological monster heads lying around, why not get creative?

And if you like incredible photos, mysterious echoes, and that thrilling “did I just feel a ghost breeze?” vibe — this place delivers. Plus, it’s right next to Hagia Sophia, Topkapi Palace, and the Blue Mosque, so you can easily squeeze it into your ancient-monument marathon.

A word of warning: surfaces can get slippery — especially around Medusa — so walk like you’re in a suspense movie. And also bring a jacket, for it gets rather chilly underground... Ready to descend into Istanbul’s past? The cistern is waiting below… just mind the water.