This small group of islands lies about 3 miles (5 km) from the nearest point on the island and is much less well known than neighbouring Staffa. The main islands in the group are Lunga, Fladda, Bac Mór, which is also known as the Dutchman's Cap, Cairn na Burgh More and Cairn na Burgh Beg. There are also numerous small islands in the group. The Treshnish Isles are now uninhabited and form a sanctuary for birds and grey seals. In the spring, Lunga is the home of thousands of nesting sea birds, mainly shag, guillemot, kittiwake, razorbill and, of course, puffin.

The best place for watching them is on Lunga, where a natural chasm separates the Harp Rock (Dun Cruit) from the main island. The sight and sound of the nesting colonies on the sheer side of the rock opposite provide an unforgettable experience, and the clear direct view could not be bettered anywhere. Late autumn is the breeding season for the Atlantic grey seals. They will often be seen around the smaller islands in the group.

The two Cairn na Burg islands have often been fortified and have ruins dating back to the Vikings and beyond.

This fossil tree was first brought to notice by John MacCulloch in 1819. It is the cast of a tree over 12m high and a metre and a half in diameter which, standing upright, was engulfed by lava and has now been exposed through erosion. During the Tertiary period, 50-60 million years ago, lava not only erupted violently from volcanoes, but also flowed more gently out of cracks in the earth's crust known as dykes. The lava flow that engulfed the tree must have been quiet enough to leave it in situ. As it cooled in formed in columns, similar to those seen at Staffa and at right-angles to the cooling surface - in this case the trunk of the tree which, indeed, exerted a sufficient drag on the lava flow to leave the columns slightly bent.

The walk out is not for the faint-hearted but there is interest every step of the way - the views are magnificent and the assemblage of geological features is unique. Buzzards and golden eagles range the cliffs and wild goats browse the talus slopes whilst a look to seaward will very likely reveal the head of a seal.

Reckoned to be the deepest in the Hebrides, this famous cave has been visited by almost everyone who has come to the island.

Boswell and Johnson visited it in 1773 and measured its depth. William Black, the popular Victorian novelist set one of the scenes of his Castle Dare in the cave. Deep inside, there is a large flat slab dubbed "Fingal's Table" and the whole cave has gathered about it an aura of mystery and magic. It was reputed having been used in very early times as a refuge for hermits - the "Culdees" of the early church used "Fingal's Table" as an altar.