The pictures below might look like The Fortress Of Solitude from the Superman movies but these incredible diamonds were actually discovered in the Naica Mine in Mexico. Mining was first started on the site to extract lead, silver and zinc but during the mining operations, caverns were discovered that contained huge selenite crystals. The ‘Cave of Crystals’ was discovered around 1,000ft below the surface and contained thousands of huge crystals, with some measuring a brain-blowing 1.2m in diameter and 15m in length! These are some of the largest natural crystals ever discovered, which led to the ‘Naica Project’ being set up to properly research the mine. Unfortunately temperatures in the cavern can reach up to 58 degrees, with 90-99% humidity, so without proper protection, people can only manage up to 10 minutes in the mine at a time.