Milecastle 42 - Hadrian's Wall

You're standing on a windswept Northumberland ridge, twenty centuries of Roman stone beneath your boots. Milecastle 42 is one of the smaller, rougher stretches of Hadrian's Wall - nothing like the polished visitor centres further west. What you get here is the genuine article: a proper Roman fortlet, about 40 metres square, with walls still waist-high in places. The stone's weathered to grey, grass grows thick between the blocks, and the wind comes straight off the Pennines.

This is a walker's attraction, frankly. You're not going to spend hours here - thirty minutes, maybe an hour if you're really into the nuts and bolts of Roman Britain. But it's the setting that makes it work. From up here you can see for miles across the moorland, and the Wall itself stretches away in both directions like a scar across the landscape. It hammers home why the Romans built it where they did.

It's free, obviously - it's archaeology, not a theme park. Haltwhistle sits just below, a proper little market town with pubs and supplies. The nearby campsites make excellent bases: Hadrian's Wall Campsite and Herding Hill Farm are both within a mile, so you could walk the Wall each day and return to a hot meal without faffing about. Combine this with Steel Rigg or Housesteads if you want the bigger picture. Families with under-tens might find it a bit sparse, but teenagers and actual history enthusiasts will rate it.