Harald Blatand’s ordered several strongholds be erected in key locations throughout the lands he ruled. One of the several known and thoroughly excavated sites is Trelleborg, Denmark.

The castle, a perfectly circular round-fort divided into quarters by two wooden roads, each quarter with four long houses, creating a perfect square, it was surrounded by a moat. Tucked in between two streams and with a moat at the base of the triangular formation along with ramparts, the soldiers easily defended the stronghold.

When first discovered historians hypothesised that the site was a Viking-era training camp, however archaeological evidence supports that entire families lived on the site. The current thought school of thought is that the forts existed to establish Harald’s supremacy as he continued to both unite Denmark and acquire new lands in Norway and Sweden.