The salt mine Slănic Prahova is part of a massive mountain of 6 km, that was formed millions of years ago, the area being at the time the bottom of a sea. The exploitation of the salt began from the time of the Roman Empire. The quantity of salt is so high that it was estimated by the experts to be eligible for exploitation for another thousand years, from now on. The modern beginnings of the mine are tied to the noble Mihail Cantacuzino that, after the acquisition of the Slănic domain initiated the first exploitation of the salt mine, between 1689-1691. The mine Slănic Prahova was also exploited by the Austro-Hungarian Empire. The work in the mine was hard and exhausting, often times the miners sacrificing their life. The tools used were rudimentary, preponderantly from hardwood, the iron not being practical enough because it would roast too fast. The chambers accessible to the public are enormous, 100 meters high and 200 meters width. The interior of the mine is colossal, imposing, fascinating and attractive, not only for a large number of tourists, but also for sick people, especially those with respiratory diseases. The mine is very similar to a museum, an incredibly impressive museum, never seen before.