Geography of the IslandAnnuvin" which was in the northwest. Mona's capital, Dynas Rhydnant, was a port-town. An unfinished seawall stretched across the harbor. Forests covered much of the island, and the Hills of Parys lay north of the capital city. There was at least one river, the Alaw, which had eroded the earth into a series of subterranean caves.
Before Princess Eilonwy was born, Mona had been the kingdom of the House of Llyr, the Sea-People, and the site of their stronghold Caer Colur. Separated from Mona by a flood, the ruins of Caer Colur were then located on a small island just offshore, to the northwest. This site seems to have been abandoned when the House of Llyr fell; this occurred some fifteen years before the setting of the novel. Apparently, the sea air and tides helped accelerate the deterioration of Caer Colur.
HistoryMagg, who took her to Achren in the ruins of Eilonwy's ancestral home, Caer Colur. Taran and the Companions, accompanied by the untalented Prince Rhun, searched the Hills of Parys along the river Alaw in order to find the princess.
Some time before the beginning of this final adventure, King Rhuddlum died. The island kingdom was inherited by his son, Rhun. After Rhun was killed in battle, Taran vowed to finish Rhun's pet project of a seawall, to protect the harbor.