The Chronicles of Narnia Wiki

Galma was a large island in the world of Narnia, located just off the coast of the Kingdom of Narnia in the exterior of the Bight of Calormen.  It was the nearest island to Narnia and was a sovereign nation.

Because it was an island, Galma remained a seafaring land even when under Telmarine control. 

During the Voyage of the Dawn Treader, the crew stopped for a week at Galma. The Duke of Galma made a great tournament for Caspian. The Duke would have been pleased had Caspian married his daughter, but nothing came of that, because Caspian found her unattractive.