That's a great pity Thoul. People making a mess is never good. Thankfully the only place I've ever found rubbish laying around is on Ben Nevis, which is to be expected from all the tourist types who go there. Seriously, who tries to climb a mountain in shorts, T shirt and sandals and carrying all their stuff in plastic bags? And it's only on Ben Nevis that you see these kind of people for some reason. Bloody weirdos. If the blisters don't force them down then the cold conditions will send them running back down.
Tanith, I don't know about light houses, I've only ever seen one and it was a really old disused one on a very small island well off the west coast of one of the western islands. However as far as castles go there are plenty to see, the most obvious ones being in Stirling and Edinburgh, the only things worth going to those places for.
Others I know of are the castle Torosay (I think) on the Isle of Mull and Fyvie castle in rural Aberdeenshire and Blair Castle in Blair Atholl. There are plenty more scattered around too, but I don't know off the top of my head. There are a few ruins to be found on Skye as well.
Anyhoo, maybe that'll temp you to see them at some point.
It's that or hiking that are the only things worth doing around here. Thankfully I got to do them before I join the masses and disappear to another country. The amount of people who leave this country every year is quite amazing but not surprising. To top it all off, a friend of mine who originally moved here from south Africa years ago can't wait to get out either, so go figure.