Staffa lies about 10 kilometres from the nearest point of Mull, and 9 kilometres N. by E. of Iona. It lies almost due north and south, is a kilometre long by about half a kilometre wide, is almost 3 kilometres in circumference, has an area of 71 acres, and its highest point is 42 metres above sea-level.
In the northeast it shelves to a shore, but otherwise the coast is rugged and much indented, numerous caves having been carved out by rain, stream and ocean. There is enough grass on the surface to feed a few cattle, and the island contains a spring, but it is currently uninhabited. During the tourist season it is visited every weekday by boat from Oban. The island is of volcanic origin, a fragment of an ancient stream of lava. In section, the isle is seen to possess a threefold character: there is first a basement, of tufa, from which rise, secondly, colonnades of basalt in pillars forming the faces and walls of the principal caves, and these in turn are overlaid, thirdly, by a mass of amorphous basalt.
Only the chief caves have been named. On the south-east coast is the Clam-shell or Scallop Cave. It is 10 metres high, about 6 metres wide at the entrance, some 45 metres long, and on one side of it the ridges of basalt stand out like the ribs of a ship. Near this cave is the rock of Am Buachaille (Scots Gaelic, The Herdsman, from a supposed likeness to a shepherd’s cap), a pile of columns, fully seen only at low tide. On the south-west shore are the Boat Cave and Mackinnon’s or the Cormorants’ Cave.
Fingal’s Cave is, however, the most famous of all. It was discovered in 1772 by Sir Joseph Banks, who visited Staffa on his expedition to Iceland. The grotto, situated in the southern face of the isle, is 75 metres long, 14 metres wide, 22 metres high and 24 metres deep at ebb. On its western side the pillars are 12 metres high, on its east 6 metres high. From its mouth to its extremity a pavement of broken pillars runs up one side. The cave is the haunt of seals and sea birds. In suitable atmospheric conditions its beauty is unique. The play of colour is exquisite, the basalt combining every tint of warm red, brown and rich maroon; sea-weeds and lichens paint the cave green and gold; while the lime that has filtered through has crusted the pillars here and there a pure snow-white. From the sombre roof of smooth rock or broken pillars hang yellow, crimson and white stalactites. The floor of the cave is the green sea, out of which the columns rise on either side with a regularity so perfect as to suggest the hand of man rather than the work of Nature. The murmur of the sea won for the cave a Gaelic name meaning “the Cave of Music.” At times of storm the compressed air, as it rushes out, produces a sound as of thunder.
When the sea is very smooth visitors may be rowed directly into the cave, but the more usual landing-place is near the Clamshell Cave, where the columns have been worn down until they form a kind of terrace running all the way to Fingal’s Cave. The Wishing Chair is formed out of a column that has broken short. From the Causeway a ladder affords access to the summit of Staffa.