Byrsa was the walled citadel above the harbour in ancient Carthage. It was also the name of the hill it rested on. The name is derived from the Phoenician word for citadel.
In Virgil's account of Dido's founding of Carthage, when Dido and her party were encamped at Byrsa, the local Berber chieftain offered them as much land as could be covered with a single oxhide. Therefore, Dido cut an oxhide into tiny strips and set them on the ground end to end until she had completely encircled Byrsa. This story is considered apocryphal, and was most likely invented because Byrsa sounds similar to the Greek word βυρσα, meaning oxhide.