Scotland doesn't lack castles and this one happens to sit in the middle of the capital city. Tough to miss it.
Edinburgh is really, really old and with age comes skeletons in the closet. One of the more sinister things you can do in Edinburgh is tour through the underground streets underneath the Royal Mile where during the great plague the city bricked up the street, developed over it and left the inhabitants to die. It also rains sometimes in Edinburgh, so this is a great indoor activity!
Greyfriars Bobby was a Skye Terrier (dog) that sat guarding his masters grave (in the adjacent Greyfriars Cemetery) for 14 years. Cool little statue of him and a bar if it rains.
Arthur's Seat is an extinct volcano that overlooks Edinburgh. It is a great hike about 1 mile east of Edinburgh Castle. It is easily reached from Holyrood Palace (Queen's official residence in Edinburgh, located at the bottom of the Royal Mile) through Holyrood Park. For an easier climb you can just walk up and along the Salisbury Crags (the cliffs around the hill). The climb gives you great views out of Edinburgh and the River Forth.
If you only take one Insta shot in Edinburgh it should probably be from the top of Calton Hill. An easy walk from Princes Street in the city center, Calton Hill has for my money the best view of the city for the least amount of walking. Lots of cool monuments, etc.
Beautiful gardens that lie beneath the castle separating the old town from the new town. Definitely worth a stroll.
During the wedding Edinburgh will be hosting: Edinburgh Art Festival, Edinburgh Festival Fringe, Edinburgh International Festival, The Royal Edinburgh Military Tattoo, and the Edinburgh International Book Festival. Each as a full program of events, from comedy shows with 10 people in the back room of a pub to the splendor of massed pipes and drums at the castle during the tattoo. One of our favorite things to do is to walk down the Royal Mile during festival time, check out some street performers, have a cocktail and then get swept along to go see a show you know absolutely nothing about!