Harpur Hill Quarry, just outside Buxton, is one of those Peak District spots that’s both fascinating and a little unsettling. Nicknamed the “Blue Lagoon” for its striking turquoise water, it looks tempting to swim in on a hot day — but don’t be fooled. The colour comes from chemicals leaching out of the limestone, and the water is full of industrial waste, dangerously high in pH, and often littered with rusting metal. Swimming here isn’t just discouraged — it’s genuinely hazardous.

Getting there: The quarry is a short drive from Buxton (postcode SK17 9JH). Parking is roadside and limited — be considerate of locals and avoid blocking access. From the road, it’s only a brief walk to the quarry edge, but the paths are uneven and not clearly marked, so sturdy shoes are a must.

What to expect: The milky-blue water is undeniably photogenic, especially when framed by the stark white quarry walls. It’s worth a quick visit for photos, but this is not a place to linger for a picnic or paddle. The site is also popular, so go early or late to avoid crowds — and be prepared for signs warning against swimming (they’re there for a reason).