What's the most obvious thing that Arthur's seat and Edinburgh castle have in common? Height.
What's the thing the Girl is most afraid of? Height.
This was an interesting couple of events for that reason.
Arthur's seat first.
It's a dormant volcano, that's somehow managed to sneak its way into the centre of Edinburgh City. Some people will have you believe that the city was built around it, but don't let those people fool you.
It is relatively benign as climbs go, taking a couple of hours up the "main path" to the summit (assuming a relatively relaxed pace and shortish legs). There are a couple of tricky parts on the main path if it's been wet, mainly due to some stretches of narrow path and a tendency towards mud. Take a good pair of boots and someone to haul you up it if absolutely necessary.
The last thirty or so metres are a bit more challenging, tending to rocky with an uneven shape, that requires a bit of a scramble and a certain amount of flexibility. Still, once you achieve it, the views of the city are spectacular.
If for whatever reason you struggle, there is an easier approach than the main path. If you wander approximately halfway round Holyrood park to the east, by Dunspie Loch, and then head offroad, there is a gentle slope most of the way to the top, which will bring you out more or less at the end of the main path, stopping just prior to rocky ground. Whether or not you should climb up that, I will leave as an exercise to the reader.
The castle is also rather high, but involves less sudden drops and more gift shops and cafes.
If my slightly hazy memory of an informative board is accurate, it's about four hundred years old (in mostly current form), and has acted as a garrison, a prisoner of war camp (Civil, Seven years, World) and if the day we visited was anything to go by, a wedding venue.
It's got a fair few exhibits in it, featuring royal family histoy, the Scots Dragoons, an excellent War museum (probably the biggest "attraction" in the Castle) and of course the Scottish Crown Jewels (or "honours"), featuring crown, sceptre and sword, which luckily survived Cromwell's attempts to get rid of a lot of the monarchy's history. They're certainly impressive pieces.
It's also got a cemetery for military dogs, which is both sad and heartwarming.
Good day out, but the castle is naturally a little expensive. Try and find a two for one. Or a friend with a Historic Scotland membership.