The Tomburg is the ruin of a hilltop castle at 316 m above sea level. NHN near the Rheinbacher district Wormersdorf near Bonn. It is located in a small nature reserve on the 316 m above sea level. NHN high Tomberg. It is a relic from the Tertiary, when liquid lava rose from the Earth’s interior and left a basalt dome after erosion of the surface layers.