Aggersborg Vikingeborg in Vesthimmerland

You're standing at Aggersborg, the largest Viking ring fortress in Denmark. Take a look around. That great, perfect circle of earth is the fortress rampart. Inside, it measures two hundred and forty metres across, and with the ditch included it's close to three hundred. What you see today is a reconstruction from the 1990s, though. It's lower than the original and mainly shows where the real wall once stood.