Basilica Cisterns, the largest surviving ancient cisterns in Istanbul, is a must-visit place for Dan Brown fans. Built in the 6th century, the cistern can hold up to 80,000 cubic meters of water and features 336 columns. The place was featured in Dan Brown's 'Inferno' and its film adaptation. Even if you are not a fan of the book or the film, the symmetry, eerie, atmospheric setting, and sheer grandeur of the place are reasons why you should definitely visit it.