I wasn't sure what to expect from the Basilica Cistern and I was afraid there might be lots of slippery stone steps to negotiate. However, this is one of those attractions which will make your jaw drop and you'll hear yourself saying ''WOW'' out loud! The entrance is unassuming and doesn't prepare you for the sight which assails your senses at the bottom of the steps (not too many steps, not slippery and easy to negotiate).
This is a vast, underground water storage tank with a high brick roof supported by 336 beautiful columns each over 26ft high with carved capitals, some ornate, some fairly plain. Look out for the carved Medusa heads which are mysteriously positioned oddly - one upside down and one on its side. Some massive fish are swimming around in the clear water and there is the constant gentle drip of water falling around you.
It's an impressive feat of engineering and it has fantastic atmosphere. This was my favourite attraction in Istanbul which is saying something when it's in competition with the Blue Mosque, Hagia Sophia, etc.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.