Ekornavallen is one of the richest prehistoric sites in Sweden. The earliest burials were made in the Neolithic period, 3000 BC. The 20 meters wide and two meters high burial mound is dated to Bronze Age (1800-500 BC). There are also lot of different kind of settings (like standing stones and stone circles) from the Iron Ages built between 0-500 AD.
The largest, and best known, of the Neolithic passage graves at Ekornavallen is one called the Girommen which according to early writers means the giant oven. It consists of sandstone slabs, but the mound which once covered the grave is entirely gone. Between the lower passage and the chamber proper lies a very large and thick slab, the "Key stone", resting on the passage stones. The grave was restored in the 1940s when a fragment of a chisel, some amber slivers and some ornate potsherds were found.
Kristiansten Fortress was built to protect the city against attack from the east. Construction was finished in 1685. General Johan Caspar von Cicignon, who was chief inspector of kuks fortifications, was responsible for the new town plan of Trondheim after the great fire of 18 April 1681. He also made the plans for the construction of Kristiansten Fortress.
The fortress was built during the period from 1682 to 1684 and strengthened to a complete defence fortification in 1691 by building an advanced post Kristiandsands bastion in the east and in 1695 with the now vanished Møllenberg skanse by the river Nidelven. These fortifications were encircled by a continuous palisade and thereby connected to the fortified city. In 1750 the fortress was modernized with new bastions and casemates to protect against mortar artillery.