Extending to 104 acres, Spike Island commands a strategic position within the sheltered mouth of the lower reaches of Cork Harbour, one of the largest natural harbours in the world.
For centuries people have used the island for a wealth of different reasons. Monasteries on islands were often hermitages and places of pilgrimage that played an important role in Early Christian Ireland, and written evidence suggests that, in the seventh century, Saint Mochuda founded a monastic settlement on Spike Island with 20 brothers.
Cork Harbour has been vital to the development of overseas trade and commerce since Viking times, but not all of the trade on Spike was legal. During the eighteenth century the rugged Spike Island shoreline was a hiding place for smugglers.
In order to protect the harbour, a series of artillery fortifications were built at strategic locations in the seventeenth and eighteenth centuries, the largest of which is on Spike Island. Unlike medieval castles, these were built with a low profile to absorb cannon fire and had the characteristic star-shaped plan with corner bastions.