In 1938, a prison and a limestone quarry were opened up side by side in Rummu. As limestone was a very important construction material at the time, the prison’s labour camp was intended to supply the mine with enough labourers for large-scale mining. Not many people were willing to become miners due to the tough nature of the job (at least without a big paycheck), so prisoners were the perfect workforce. The mine slowly lost its importance by the 1970s because building materials had changed and prisoners were used as workers in other industries. Rummu quarry also has a 70-metre hill next to it made of limestone mining leftovers.
Water constantly needed to be pumped out of the quarry, but as production levels dropped, the pump was turned down to pretty much meet the minimum needed not to flood the prison. In the 1990s, the pump was completely shut down. This flooded the quarry so quickly that there’s still a giant excavator, other equipment and buildings in the middle of what is now a crisp, clear, turquoise lake. These days it’s a popular swimming spot in summer.