We went on the Mercat tour called Descend and Discover ( http://www.mercattours.com/m/descend-and-discover.asp) a week ago, which is self guided. You get a map of the vaults and a flashlight, and get to walk around in your own tempo, no one dressed up and no one trying to scare you.

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Others might disagree but in my experience, Mary King's Close is more of a a real thing, and whilst they have actor/guides who explain it to you and can put a creepy supernatural spin on things for fun (it is an underground hidden street after all), the Close was actually real with some documented evidence of the people living there and what they did. Some of the vaults guides are more supernatural focussed and whilst the vaults are also definitely real places with some history, their tours are usually a bit less factual and far more spooky. You can take your pick about which of them (or both) you want to experience. More on reddit.com

Well Mercat Tours is the first and the only 5 star tour company in Edinburgh, and they have exclusive access to the most extensive set of vaults of the South Bridge. The Ghost and Ghouls tour is only £14 per adult and is 2 hours of gory and real history and includes drinks in their underground Cellar. The Hidden and Haunted tour is the adult only 1hr tour which is £11 and includes paranormal happenings in the vaults. The newest tour they have is the Doomed, Dead and Buried tour, it goes to the underground and the Canongate Graveyard. Here is their official website. My source is my girlfriend Victoria who works for Mercat so again, slightly biased! I personally have been on a bunch of the tours and had a brilliant time and the guides are fantastic. Edit: TripAdvisor More on reddit.com

Full disclosure: I worked for two of three 'main' tour companies (and have friends in others) for about 15 years. If you want history: Mercat Tours (daytime). Their night tours are good too, but I found some of the guides to be a bit "Am-Dram". Of the three underground tours, their vaults are probably the most impressive. If you want "Ooo! Spooky!": Auld Reekie Tours. Cool underground tours. Genuine, working pagan temple inside. If you want awesome, scary comedy fun: The Witchery tours Longest running tour, I believe. It's a good fun blast, while walking around the old town. If you want first class, professional storytelling that's both funny and terrifying: City of the Dead tours. The graveyard tour is probably the best. They also do an underground tour, and a "double" tour that goes to both areas (vaults and Greyfriars graveyard). Each guide is slightly different (no fixed script) but they're all awesome. If you want usurpers who utilise unfair business practices, advertise "free" tours, and send their recruits on other tours to steal stories (and jokes), then tell them wrong: Try Sandemans. The guides are good folk, probably, but the company sucks ass. Some of the other free tours are actually pretty good. Also, special mention to the Edinburgh Pub Crawl. More on reddit.com