Windsor Castle

The walk up Castle Hill from Windsor town centre is steep enough to get your calves burning, but then the whole point hits you - a proper medieval fortress still very much in use, not just gathering dust in a museum. Windsor Castle sprawls across 13 acres, a working royal residence where you can actually see the flagstaff change when the monarch's in residence. State rooms open to the public show off centuries of royal collecting, from old masters to furniture that makes you understand why "priceless" is more than just a word. St George's Chapel is the real knockout - late Gothic architecture that takes your breath away, and the final resting place of ten monarchs including Henry VIII.

Admission isn't free, but it's worth budgeting for if you're doing a proper park holiday around the area. Allow a solid three hours minimum, more if you're genuinely interested in the interiors. Families with under-eights might find the self-guided route a slog, though older kids who like their history get genuine value. Go midweek in shoulder season if you can stomach the drive - summer Saturdays turn the courtyard into a car park queue.

Staying at Queens Acre or Amerden puts you within a few miles, so you're talking a quick drive rather than a day trip from halfway across the county. The Thames-side setting is lovely for a wander after you've done the castle, and Windsor's got enough tea shops and riverside pubs to pad out an afternoon properly.