Fingal's Cave Fingal's Cave Fingal's Cave is a sea cave on the uninhabited island of Staffa, in the Inner Hebrides of Scotland, known for its natural acoustics. The National Trust for Scotland owns the cave as part of a National Nature Reserve. It became known as Fingal's Cave after the eponymous hero of an epic poem by 18th-century Scots poet-historian James Macpherson. Fingal's Cave is formed entirely from hexagonally jointed basalt columns within a Paleocene lava flow, similar in structure to the Giant's Causeway in Northern Ireland and those of nearby Ulva. In all these cases, cooling on the upper and lower
Cave of the Crystals Cave of the Crystals Cave of the Crystals or Giant Crystal Cave () is a cave connected to the Naica Mine at a depth of , in Naica, Chihuahua, Mexico. The main chamber contains giant selenite crystals (gypsum, CaSO·2 HO), some of the largest natural crystals ever found. The cave's largest crystal found to date is in length, in diameter and 55 tons in weight. When it was accessible, the cave was extremely hot, with air temperatures reaching up to with 90 to 99 percent humidity. The cave is relatively unexplored due to these factors. Without proper protection, people could