Þrístapar, also known as Three Mounds, is the site where the last public execution in Iceland took place on January 12, 1830. Agnes Magnúsdóttir and Friðrik Sigurðsson were beheaded as punishment for their crime of double murder.
Þrístapar is located close to the road, with a parking area (GPS: 65.501125, -20.398430) from where you can reach the site in about 5 minutes.