After Oppenheim was returned to the Empire in 1147, it became a Free Imperial City in 1225, during the Staufer Emperor Frederick II's reign.

[clarification needed] On 14 September 1620, Spanish troops overran the town in the Thirty Years' War.

In March 1945, troops of the 3rd Army under General George S. Patton managed to build a crossing over the Rhine near Oppenheim and to occupy it.

To revive this wine sponsorship and to give thanks for the commitment to the town of Oppenheim, the Governing Mayor of Berlin, Klaus Wowereit, was “knighted” on 11 March 2006 by Mayor Marcus Held, earning the title of "Wine Knight" (Weinritter).

The sponsorship has found active expression in, among other things, the town's participation in the estate festivals held by the Senate of Berlin in 2007 and 2008.

At the invitation of Berlin's governing mayor, Klaus Wowereit, a citizens’ delegation, under Mayor Marcus Held, took part in the festivities at the German Embassy in Paris on German Unity Day, as well as during the jubilee celebrations of the Berlin-Paris city partnership.

Underground passageways, stairways and rooms link the houses and facilities with each other on a number of levels.

The exact extent of the passageways is still not known with any great certainty, despite investigations commissioned by the town, but the length is estimated to be at least 40 kilometres (25 mi).

Guided tours through this unique underground labyrinth are offered all year round by the town's Tourism and Festival Play Bureau.

Locally it serves foremost as a link to the nearby cities of Mainz and Worms and the Mainzer Autobahnring in the north and A 6 in the south.

Furthermore, ORN regional bus routes run from Dalheim to Wörrstadt by way of Oppenheim and towards Guntersblum and Undenheim.