The Rodderberg is an extinct volcano in the east of the municipality of Wachtberg near Bonn, Germany. The last eruption was 250,000years ago.

It is situated just above the Rhine valley. Together with the Drachenfels directly opposite, the Rodderberg narrows the Rhine valley. This gorge portion is the southern limit of the lowland-bay of Cologne.

The Rodderberg offers views to the Siebengebirge, the Rhine valley and up to the Cologne Cathedral, about 50km away.

Geology

The Rodderberg detonated in a phreatomagmatic eruption about 250,000years ago. This happened when the magmatic plume reached the groundwater level of the Rhine (about 50m higher than today). After the explosion, the crater was filled with water that formed a maar of about 90m depth. In the last 250,000years this feature filled with dust and soil until it was filled up to today's level.

The Rodderberg is now a small hill that has a shallow concave shape.

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