[1] It has the southernmost mainland point of Svealand, the middle of the three lands of Sweden.
Alongside it a few kilometres eastward, there are several reservoirs around Gälkhyttan, near the border to the Tuna district to the north.
This part is more agrarian with farmlands surrounding the second largest settlement of Buskhyttan.
The modern road instead goes straight through the rural parts between Nyköping and Nävekvarn.
Tunaberg used to be a single municipality but have since the merger into Nyköping Municipality in the early 1970s been divided into two separate electoral districts: Koppartorp and Nävekvarn covering the eastern and western parts respectively.