Oldtown is one of the biggest cities in Westeros, and easily the oldest. It was built by the First Men, before the Andals invaded Westeros. It is located in the Reach, and is the western terminus of the Roseroad from King's Landing to Highgarden. It is the seat of House Hightower. It is also the location of the Citadel, the home of the Maesters who serve the noble families of Westeros, and the realm.
The current head of House Hightower is Leyton Hightower.