speaking of I've always wanted to visit Waterloo assuming it's relatively maintained which, considering the havoc WW1 wrecked on the landscape in Belgium is probably not the case.
Not ruined by WWI (most of the WWI damage was in a pretty narrow corridor along where the trenches stagnated), but as I understand it, pretty heavily landscaped with memorials.
But thinking of that, the WWI trenches have always been something I've wanted to see. They're mostly still there with different levels of collapse and growth, but there are old redoubts and whatnot that are just scattered all over that still have soldier art and even stuff abandoned in place in them.