Longford Castle

You'll spot this triangular red-brick fortress from miles away across the Wiltshire landscape - an absolutely mad piece of architecture that looks like someone flipped a traditional castle on its head. Built in the 1580s by William Paulet, Longford Castle sits on a peninsula jutting into the River Nadder, and the unconventional triangular layout was genuinely meant as some grand statement about geometry and Renaissance thinking. Fair play to the man's ambition, even if it does look rather odd.

The castle itself remains a private residence, so you can't wander inside, but the exterior and grounds are worth a proper look if you're passing through Salisbury. The setting is genuinely lovely - you can walk the riverside paths and take in the architecture from different angles, which is where it actually starts to make sense. It's the sort of place that takes about 30 minutes to an hour if you're the type who enjoys the odd detour. Photographers will find plenty to work with, especially in late afternoon light.

It's not a major draw on its own, but if you're camped at one of the nearby sites - Summerlands gets consistently strong reviews - it makes for an easy drive or decent cycle ride. Combine it with a morning exploring Salisbury Cathedral and you've got a solid half-day sorted. Free to view from outside, obviously. The bit that grates is the private status - you're essentially rubbernecking from the perimeter - but the unusual design makes it worth stopping for if you're in the area.