Going down the steps into the Basilica Cistern is the closest thing Istanbul has to changing worlds in thirty seconds. Above is the noise of Sultanahmet; below, a forest of columns, shallow water, and the sound of drops falling into it.
The cistern was built under Justinian in the sixth century and held water for the imperial palace. Its three hundred and thirty-six columns were reused from older ruins, and two of them rest on Medusa heads whose placement has never been explained.
Lighting and walkways make it an easy visit, and the cool air is welcome in summer. From Romance Istanbul Hotel it is about ten minutes on foot; going late in the afternoon, when the tour groups thin out, gives you the quiet the place deserves.