Cornhill Castle (site of)

There's not much left standing at Cornhill Castle these days - just earthworks and a scatter of stones on a rise above the River Tweed near Coldstream. But that's rather the point. This is proper archaeology: you're reading the landscape rather than gazing at manicured ruins.

The site itself dates back to the 12th century, when it was a significant stronghold. Now the castle exists mostly as a series of banks and ditches that once formed its defences. Walk the perimeter and you can trace the outline of what was here - the inner ward, the ditch system, the way it commands the valley below. It takes maybe thirty minutes to properly explore, longer if you're the sort to sit and sketch or photograph.

Historically-minded walkers get the most from this. Families with young children might find it less engaging than an actual standing castle - there's limited drama when it's mostly grass and bumps. But if you're doing the Borders walking circuit and passing through Coldstream anyway, it's worth the short detour.

There's no visitor centre or facilities. Spring through autumn is when you'll see it best, when the grassland's not waterlogged and the earthworks cast proper shadows in the light. Coldstream Holiday Park sits just 1.5 miles away, so you could easily tack this onto a broader park stay, combining it with riverside walks and the town itself. Free, naturally - it's just land.