Thus Eorl became the first King of the Mark, and he chose for his dwelling a green hill before the feet of the White Mountains that were the south-wall of his land. There the Rohirrim lived afterwards as free men under their own kings and laws, but in perpetual alliance with Gondor.
- Appendix A, The House of Eorl
The first capital of the kingdom of Rohan, Aldburg was erected by Eorl the Young, the first king of the Mark. After the founding of Edoras, the kings of Rohan ruled from its Golden Hall and Aldburg became home to a side branch of the royal family, a member of whom holds the title of the Third Marshal of the Riddermark. The current head of this branch is king Théoden's nephew, Éomer.
Built around an old Gondorian stronghold sat on top of a green hill, the city is further fortified by multiple rows of ditches, ramparts, and palisade walls which were continuously added as the city grew throughout the centuries. This makes the city not only a key defensive position but also the chief gathering place for the riders of the Eastmark.