The Drachenlauf (Dragon Race) takes place every October near Bonn, Germany. Thousands of runners have completed the 25km circuit course with 1,050m vertical gain. Start and Finish are at Gut Buschhof (address: Zum Buschhof 30, 53639 Königswinter). Current record for single completion is 01:51:57, set in 2018 by Moritz auf der Heide.

No one however has attempted to complete this highly demanding course (incl. some long 15% climbs) twice in a row, back-to-back.

Het Graafschapspad

The 'Graafschapspad' is a regional path with a length of 125 kilometers through the Achterhoek. The route is marked with yellow-red signs in both directions. The path starts in Zutphen at the St. Walburgskerk and can therefore be walked in either direction, clockwise or counterclockwise. De Graafschap owes its regional name to the former county of Zutphen, a union of noble families, castle lords and cities. The literal translation of the dutch word 'graafschap' is county. 

A dirt loop that roughly parallels the course of the old Morgul Bismark road race.

From: https://www.trailrunproject.com/trail/7048586/red-rocks-and-dakota-ridge-loop: