The saga entitled "Kjalnesingasaga" tells of an Irish widow named Esja. Esja was very wealthy and lived on a farm. Much doubt has been cast on the historical veracity of this saga and the true origin of the name remains obscure.

However, Esja is a mountainous mass near Reykjavik covering an area so large that each side of the mountain has its own particular characteristics. The residents of Reykjavik consider Mt. Esja their own. Interest in outdoor activities on and near Esja have been increasing markedly, including ice climbing up frozen waterfalls!

Well-marked trails lead up to Thverfellshorn, a trek that takes between one and three hours.