To get to this place from Dortmund Hauptbanhof (central station), you need to get on the U41 subway line in direction of Hörde, hop off at Hörde Banhof station and get on the 442 bus in direction of Syburg, hopping off in the last stop, Syburg. From there it is just a quick walk to the park, the ruins and the monument. Google Maps somehow does not know of this route, that takes about 40min. The whole place is very beautiful and the view is amazing, even in a cloudy day. There are small hiking trails into the woods, and it is difficult to get lost there. Give it a try!