This is another highly recommended historical site! The old city layout resembles a human spine and ribs, with the spine being the main road, the Royal mile, and the ribs being the offshoot streets called "closes." These closes are really more like super thin alleyways, and the people lived and worked to the sides of the closes. Edinburgh used to be slanted towards the castle, pyrimidally, and the closes would run downhill until they hit the Nor Loch (now Prince's St Gardens), where the rich people lived as high up as possible, since people would dump their sewage down the closes to let it run into the Loch. So, when the city decided to build the Royal Exchange, they wanted it to be flat, so they razed over the old closes, and built on top of them, to flatten it off. To do this, they razed and filled in some of the closes, but they used the structure of some of the others to help support the foundation of the exchange. Mary King's close is one of those left as support, and this tour lets you wander around in the well preserved close, (which is a truly slanted alley) below ground! You get to see a low house, a rich person's house (which has preserved the printing on the walls!), a butcher's, sawmaker's, etc. It's a really great historical tour, and the guides are very entertaining in the way they tell the stories. You can't take any pictures down there, so I took this one to commemorate the fun tour.
