Four roof slate benches from 2 to 20m thickness lay in the Iberg. They belong to a ca 400 million years old chalk and slate formation.
In 1864 the mining started in adit 1. The winning of slate was done by blowing up with gun powder. With that one got big blocks that were fragmented with wedges and hammers into transportable pieces.    
The operation was closed down in the year 1971 due to un-profitability and the mine was opened to the public.

The enormous mining rooms arouse again and again the visitor's amazement. All cavities that are below the adit level have filled with water and are not accessible any more.  
A visit under specialist guiding (from 8 persons) is for everybody an unforgettable event. Don't forget your warm jackets as the air sweeps with  6-8 degree through all pits, good for asthmatics.