The Blue Lagoon – Harpur Hill.

The Blue Lagoon located at Harpur Hill, near Buxton, Derbyshire, England is also known as the Hoffman Quarry, was once a limestone quarry. From 1835 to 1952, limestone extraction took place here, producing quicklime used in steelmaking.

The quarry’s vivid turquoise blue waters attracted tourists due to finely dispersed calcium oxide particles, a byproduct of the quarrying process.

The Blue Lagoon. Photo by Gary Tacagni.

Beneath the inviting surface lies a toxic soup. The lake’s pH is an astonishingly alkaline 11.3 (for reference, ammonia has a pH of 11.5, and bleach has a pH of 12.6). The quarry was also used as a depot for storing chemical weapons during both World Wars.

Signs around the lagoon warn visitors of its dangers: “Polluted water. Lagoon known to contain: Car Wrecks, Dead Animals, Excrement, Rubbish.” Swimming in the Blue Lagoon can cause skin and eye irritations, stomach problems, and fungal infections.

Despite the warnings, families visited the lagoon, and children swam in its turquoise waters. Locals have tried to deter swimming, but the draw remains strong. The limestone rocks leach calcite crystals into the water, turning it green while retaining its allure.

In 2013 the county council took action by adding black dye to the water to deter swimmers. Although effective, the dyeing process needs to be repeated every few years as the water reverts to its enticing turquoise hue.

The Blue Lagoon is no longer blue due to regular dyeing. The best time to visit is from January to March for photos after the dye has faded.

Note there are no public footpaths leading directly to the lagoon, so avoid trespassing on private land. In summary, the Blue Lagoon’s beauty masks its toxic nature, a reminder that appearances can be misleading.

Calcium deposits below Harpur Hill. Photo by Gary Tacagni.