Found under the Eminönü district of Istanbul, the Basilica Cistern is a 6th century underground chamber that features 336 marble columns, vaulted ceilings, and arched doorways, all made without a mold – incredible when you consider that it was built in 532CE. This is the place where 80,000 cubic meters of water were stored for use in the nearby Great Palace and surrounding buildings. After part of the cistern was destroyed and covered by dense construction during the Byzantine and Ottoman periods, it was rediscovered in 1545. Since then, the location has been restored to its original condition – even though the Great Palace no longer stands.
When to go: Its underground location make the Basilica Cistern a great place to cool off during the summer months; if you go on a rainy day, the stairs can get slippery, so watch your step. Head over to see the chamber while in the Stoa Basilica Square or drop by after you've finished seeing the Hagia Sophia, which is right next door. The cistern can be explored in about 30 minutes.
What to do: While observing the beautiful symmetry of the columns, make sure you head to its northwest corner to check out the upside down Medusa heads that support two columns. There are also columns in the center of the cistern with an intricate and unique teardrop design. Before you leave, grab a cup of cay, a Turkish coffee drink, at the café near the exit. Rumor has it that these are some of the best coffee blends you can get in Istanbul. Admission into the cistern is about $5.