The salt deposit in the Prahova region in Romania is so unimaginably deep that there are actually two mines vertically stacked beneath the town of Slănic. The upper-level Mihai mine operated from 1912 to 1942, creating a 66-meter high cavern, while the lower-level Unirea mine operated from 1943 until 1970, creating a 52-meter high cavern. The two levels are separated by a 40-meter thick floor of salt.
Since mining ceased due to lack of profitability, the Unirea mine has been transformed into a public tourist destination, open seven days a week. It now features kid-friendly attractions such as basketball courts, pedal-powered go-karts, and mini-golf. However, these activities are completely overshadowed by the gigantic caverns in which they are situated.
The walls you see in all these photos are not rock; they are salt, the same type that was excavated many years ago. If you lick the wall, it's salty taste confirms this. Layer patterns decorate every surface, showcasing the salt's varying levels of purity.
If you look closely at the photos, you will also notice yellow-brown stains on most of the walls. These is where oil has seeped into the salt during cutting, stains left by the large metal chainsaws used for excavation. These machines were used to excavate the Unirea mine resulting in trapezoidal chamber profile. Starting at the top and working downwards, 2.2 meters at a time, a 10-meter wide level was excavated to set the template for future work. Next, salt was excavated level by level at a 60° angle for the next 20 meters, widening the floor plan and creating a structurally sound ceiling. Finally, more layers were dug straight down until the mine closed, forming the floor level that visitors can walk on today.
High on the cavern walls, remnants of past these works can be seen: staircases leading to nowhere, doors without destinations, and walkways on the ceiling.
