Cowdenknowes Reservoir

The water here sits quietly between rolling hills, surrounded by nothing but moorland and the occasional Scots pine - proper remote for somewhere so close to Helensburgh. Cowdenknowes Reservoir isn't a tourist hotspot, which is precisely why it's worth the drive. You get walking trails that loop around the water's edge, though the paths can be boggy after rain, so good boots are essential.

This is walkers' territory. The reservoir itself won't take you longer than an hour to circumnavigate, but that's the point - it's a gentle half-morning thing, not an all-day expedition. There's no cafe, no visitor centre, no facilities to speak of. You come here for the quiet and the chance to spot red grouse or, if you're lucky, golden eagles overhead.

Families with young kids might find it a bit bleak and featureless compared to a proper loch, but teenagers and serious hikers will appreciate the genuine remoteness. In winter it can feel properly wild; in summer the midges can be fierce, so time your visit accordingly.

The nearest proper base is Helensburgh, just three or four miles away, though both Rosneath Castle Caravan Park and Hunters Quay Holiday Village offer decent spots for staying put. This works well as a morning walk before heading down to the coast, but it's not something you'd structure an entire day around. Free access, naturally - there's literally nothing here to charge for.