In 1990, mining stopped at a 55-metre-deep Swedish limestone quarry; a year later...

55-meters-deep Swedish limestone quarry When mining stopped at an isolated limestone quarry in central Sweden in 1990, the local area was left with a 55-metre-deep industrial pit cut into the pine forests outside Rättvik. Just a year later, a former opera singer discovered that the abandoned quarry had remarkable natural acoustics. Today, the former mining site has become Dalhalla, an internationally known open-air concert venue that attracts more than 100,000 music fans to Dalarna every summer.A geological crater shaped by an ancient impactAccording to geological information about the area, the site that became Dalhalla was shaped by a huge meteorite impact around 360 million years ago. A meteorite about four kilometres wide struck the Earth and created the geological formation now known as the Siljan Ring. The impact changed the local rock formations, bringing ancient layers of limestone closer to the surface. According to historical accounts of the quarry, commercial mining began at the Dräggängarna site in the 1940s, with companies removing millions of tonnes of limestone over several decades. When mining finally stopped in 1990, workers had created a huge natural bowl about 40...