Ojamon Helmi / The Pearl Of Ojamo — Geocache of the Week

by famsten
N 60° 14.222′ E 024° 02.194′

Any abandoned mine sounds like an interesting place for a geocache, but the Ojamo mine in southern Finland is more than just that. The mine is completely submerged in water and still contains tracks, elevators, tools, test samples, and drilling equipment systems from when it was fully operational.


The Ojamo mine is near the city of Lohja, about an hour from Helsinki, Finland. The mine opened for business in the early 1920s. Eventually they created miles of complex tunnels that reach depths of around 240 meters (800 ft).

This D5/T5 takes serious scuba diving skills to safely and successfully locate the geocache. The cache is located inside the “Pearls” — named after a long tunnel that connects several halls and narrow passageways.

Carefully navigate underwater around a depth of 55 meters (180 ft) through the passages and find a small cavity containing a pocket of air where geocachers Luttu and famsten placed the cache. The air in the pocket is not breathable as it can contain a high concentration of carbon dioxide. “Nevertheless, safety is always number one, and every diving team must have solid plans, safety measures and surface support in place before any dive,” says Luttu, who assisted in the planning and placement of this cache. 

Would you dive underwater for a geocache?

Continue to explore some of the most amazing geocaches around the world.
Check out all of the Geocaches of the Week on the Geocaching blog. If you would like to nominate a Geocache of the Week, fill out this form.

Andrew the Manager of Community Engagement at Geocaching HQ. He is typically laughing at his own jokes, getting into mischief with Signal, or looking for the next adventure.