Fingal's Cave is a sea cave on the uninhabited island of Staffa, in the Inner Hebrides of Scotland, part of a National Nature Reserve owned by the National Trust for Scotland. It is formed entirely from hexagonally-jointed basalt columns, similar in structure to (and part of the same ancient lava flow as) the Giant's Causeway in Northern Ireland, and those of nearby Ulva. In both cases, the cooling surface of the mass of hot lava cracked in a hexagonal pattern in a similar way to drying mud cracking as it shrinks, and these cracks gradually extended down into the mass of lava as it cooled and shrank to form the columns which were subsequently exposed by erosion.
Its size and naturally arched roof, and the eerie sounds produced by the echoes of waves, give it the atmosphere of a natural cathedral. The cave's Gaelic name, Uamh-Binn, means "cave of melody".
The cave was "discovered" by 18th-century naturalist Sir Joseph Banks in 1772. It became known as Fingal's Cave after the eponymous hero of an epic poem by 18th-century Scots poet-historian James Macpherson. It formed part of his Ossian cycle of poems claimed to have been based on old Scottish Gaelic poems. In Irish mythology, the hero Fingal is known as Fionn mac Cumhaill, and it is suggested that Macpherson rendered the name as Fingal (meaning "white stranger") through a misapprehension of the name which in old Gaelic would appear as Finn. The legend has Fionn or Finn building the causeway between Ireland and Scotland.
The cave has a large arched entrance and is filled by the sea; however, boats cannot enter. Several local companies include a pass by the cave in sightseeing cruises from April to September. However, it is also possible to land elsewhere on the island and walk to the cave overland, where a row of fractured columns form a walkway just above high-water level permitting exploration on foot. From the inside, the entrance seems to frame the sacred island of Iona across the water.
This is the Scottish end of the Giants Causeway...
Legend has it that the Irish warrior Fionn mac Cumhaill (Finn McCool) built the causeway to walk to Scotland to fight his Scottish counterpart Benandonner. One version of the legend tells that Fionn fell asleep before he got to Scotland. When he did not arrive, the much larger Benandonner crossed the bridge looking for him. To protect Fionn, his wife Oonagh laid a blanket over him so he could pretend that he was actually their baby son. In a variation, Fionn fled after seeing Benandonner's great bulk, and asked his wife to disguise him as the baby. In both versions, when Benandonner saw the size of the 'infant', he assumed the alleged father, Fionn, must be gigantic indeed. Therefore, Benandonner fled home in terror, ripping up the Causeway in case he was followed by Fionn.
Another variation is that Oonagh painted a rock shaped like a steak and gave it to Benandonner, whilst giving the baby (Fionn) a normal steak. When Benandonner saw that the baby was able to eat it so easily, he ran away, tearing up the causeway.
The "causeway" legend corresponds with geological history in as much as there are similar basalt formations (a part of the same ancient lava flow) at the site of Fingal's Cave on the isle of Staffa in Scotland.