MoM - Miniera Olgiate Molgora - Level 1

The dive

This is a flooded mine, not a dive site in the ordinary sense. The Gallerie Pelucchi at Olgiate Molgora in the province of Lecco were dug for marl to make Portland cement: excavation began in 1906, cement production in 1908, and the works ran until an explosion and fire on 3 June 1967 killed six workers and ended the operation. The mine goes down five overlapping, near-parallel levels connected by a reinforced-concrete shaft. Digging past about 60 m hit groundwater, which was held back by constant pumping; when the pumps stopped, the four lower levels flooded, and that is what is dived today.

'Level 1' in the name is the first flooded gallery, not a certification grade. It is 225 m long, 10 to 11 m high and 9 to 10 m wide, and it sits between the surface and about 11 m in summer, or 6 to 17 m in winter, because the water table moves several metres with the rainfall. It is the shallowest and least demanding part of the mine, which is precisely why it is used: cathedral-sized volumes at trivial depth make it a serious place to work on buoyancy and trim over long dives. Below it, level -2 runs 15 to 32 m, level -3 31 to 48 m, and level -4 as deep as 66 m in winter.

The rules are the site. Every dive is guided, and the first two dives are always guided regardless of experience. The maximum group is five people including the guide, seven with a guide and a tail assistant, and the group is rated at the level of its least-qualified diver. To enter you must present a cave or mine certification from a recognised agency matching the profile, logbook evidence of cave or mine experience, a doctor's medical certificate and cave-diving insurance, then present and sign a dive plan including a rescue plan and sign a liability release. Minimum equipment includes a dry suit, a wing of at least 20 litres of lift, a manifolded twinset carrying at least 4,000 litres of gas or a CE-certified rebreather suitable for cave use, one main light plus two backups, two spools of at least 20 m and two line cutters. Sidemount is welcome but is not required: the galleries are large. The mine is laid with fixed lines and navigational signs, but excellent navigation is explicitly stated as mandatory, because this is a three-dimensional labyrinth crossed by shafts and ventilation holes rather than a single tunnel.

Physically it is stable and cold-ish: water a constant 13 to 14 C year-round, gallery air 17 to 19 C, no current, visibility from crystal clear to milky depending on rain, season and how the divers in front of you swim. Every gallery floor carries 5 to 20 cm of marl powder, so buoyancy control is not a nicety. Entry is a walk-in of less than 15 m from the car park over flat ground and stairs, with electric cranes to move tanks and rebreathers. A colony of protected bats, Myotis capaccinii and Myotis nattereri, roosts 300 to 400 m from the entrance; nothing may be removed from the mine and diving is contactless.

Certified open-water divers who are not cave divers have exactly one way in: the operator's Discover Mine Diving trial, run with an instructor, starting in the cavern zone and going a short way into the mine proper if the diver is comfortable. Outside that programme, recreational divers do not dive here. One practical warning: the operator's website no longer resolves, so everything above comes from archived copies of its own pages and documents from 2021 to 2023. Confirm the mine is still taking bookings before travelling.

• The first flooded gallery: 225 m long, 10-11 m high, 9-10 m wide, surface to about 11 m in summer
• Constant 13-14 C water and 17-19 C gallery air, year-round, with no current
• Fixed lines and navigational signs throughout, but a genuine three-dimensional labyrinth
• Walk-in entry under 15 m from the car park, with electric cranes for heavy kit
• Protected bat colony 300-400 m inside; nothing may be removed

Conditions

Constant 13 to 14 C water and 17 to 19 C air in the galleries, year-round, with no current. Level 1 runs from the surface to about 11 m in summer and from 6 to 17 m in winter as the water table rises. Visibility is crystal clear to milky depending on rain, season and diver behaviour, over 5 to 20 cm of marl powder on the floor.

On current: No current in the flooded galleries. Visibility ranges from crystal clear to milky depending on rain, season and diver behaviour, over a floor carrying 5 to 20 cm of marl powder. Depths on level 1 shift with the water table: about 0 to 11 m in summer and 6 to 17 m in winter; we record the winter maximum as the conservative figure.

Dives & underwater footage

Life at MoM - Miniera Olgiate Molgora - Level 1

This is fresh water, so there is no reef life to log. We do not carry an occurrence record for inland sites: the scientific databases we use are marine, and the nearest records would come from whatever lake or river is in the search radius rather than from the water you dive.