Aldburg, meaning "Old Fortress", was the original seat of the Kings of Rohan, recorded as the home of Eorl the Young. After the King's seat moved to Edoras, Aldburg remained a place of noblemen, and it also become the centre of military activity in the Eastfold. In the time of the War of the Ring, it was home to first Éomund and then his son Éomer, both having the rank of Third Marshal of the Mark.

Aldburg was located in the Folde.

[with additional information from Electra_Calen]