Castle Hymel

The ruins of Castle Hymel stand just outside Corby, a proper slice of medieval Northamptonshire that most people drive straight past. What remains are fragmented stone walls and earthworks - nothing you'd mistake for a grand castle tour, but enough to grip you if you're into the bones of England's past. It's the sort of place where you can actually stand in what used to be someone's hall and feel the weight of six centuries.

Historians and serious walkers will get the most from this one. Casual visitors might find themselves disappointed after twenty minutes. The site requires a bit of detective work - you're reading the landscape as much as looking at stones - which makes it ideal for anyone who prefers thinking on their feet to guided commentary.

Castle Hymel works brilliantly as a half-hour detour between park days. New Lodge Farm Bulwick is barely a mile and a half away, so if you're based there, you could easily pop over before breakfast. Rockingham Forest Park lies just four miles south, meaning you could string together a morning of old Northamptonshire without much faffing about. It's free to visit and there are no opening hours to worry about - that's the beauty of ruins.

Bring proper walking boots. The ground gets boggy after rain and there's no visitor infrastructure whatsoever. Not a visitor centre, not a café, not even a bin. That's either utterly brilliant or completely pointless, depending on what you're after.