We were able to check out Craigmillar Castle with our Historic Scotland pass. If you’re visiting Edinburgh for more than a few days, it’s an easy 3 mile trip from the city centre. Personally, I prefer Craigmillar Castle more than Edinburgh Castle, just because tickets are cheaper (£5.50 for 1 adult) and I enjoy exploring medieval ruins more than visiting museums.
Historically, Scottish nobility took breaks from living in Edinburgh Castle or Holyrood in Craigmillar Castle. Most famously, Mary Queen of Scots was a frequent visitor and even fled there after the murder of her secretary. It’s well preserved, but mostly in ruins. You can still walk through its passageways and climb the Tower House for nice views of Edinburgh. It’d be super fun to play hide and seek or even laser tag in here, although I’m pretty sure someone will get hurt.
More importantly though, Craigmillar Castle is dog-friendly so we took Blue here.