Gronligrotta

Gronligrotta is located in Nordland, Norway close to the town of Mo I Rana. It consists of a maze of passages totaling more than 4 km in length and carved in a marble stripe at the contact with a micaschist formation. It is the only cave in Norway fitted with electric light. The visitation flow is uni-directional, i.e. tourists use different entrances to enter and exit the cave respectively. Cave lighting uses incandescent "economic" bulbs which led to moderate growth of  lampenflora on some walls. Two monitoring stations have been installed in the cave using central dataloggers and up to 4 temperature/RH sensors each + CO2 sensors and traffic counters.

Gronligrotta, station 1 - note the temp/RH sensor and the CO2 + people counter box initially located on the ceiling.

Gronligrotta, monitoring station 2