Międzyrzecki Rejon Umocniony launches Poland's sole underground bike trail

The Międzyrzecki Rejon Umocniony (MRU), one of the largest fortification systems in Europe built from 1934, has opened a 30‑kilometre underground cycling route that runs through historic bunkers and tunnels. The trail, the only one of its kind in Poland, is equipped with lighting, ventilation and signage to ensure comfort and safety for cyclists exploring the former German defensive complex.

Visitors can see preserved Panzerwerki, anti‑tank barriers known as “dragon’s teeth,” and technical rooms while riding beneath the ground. The MRU also serves as a major wintering site for bats, one of the largest in the country, leading to occasional temporary closures of certain sections to protect the wildlife.