Eilean Mor is the largest of the two islands in Loch Finlaggan which are the administration centre for the whole of the Lordship of the Isles and its territories. Unlike the neighbouring island, it is connected to the paved roads of Islay by a causeway, which mean that this island is also far more accessible.

It is partially man-made, but the fortifications and chapel are on the original ground. The great hall, the entry hall, and the piers are all built on the area where an accumulation of building material has added another third to the island, and they are just as lavishly decorated as the buildings on Eilean na Comhairle.

This island has many purposes. It is the first part of Eilean na Comhairle's defences, provides accomodation for many of the retainers of the Lord of the Isles, is an alternative place for feasting and entertainment if the Lord of the Isles does not wish to use his own house for such purposes, and is also the sacred place of worship where the Lords of the Isles attend services in the presence of many of their ancestors.