Speleology and space flights are significantly equivalent from a certain point of view. There is not that big difference between a speleologist deep inside a cave and an astronaut situated in space - both discover unknown spaces, species or organisms and enter places where literally nobody has gone before. For both the journey back to the surface of the planet Earth requires spending hours or days of a risky and perilous effort. This parallel is particularly true for cave divers, due to additional barriers imposed by the aquatic element - such as high pressure environment, unpredictable underwater currents, restricted visibility, and limited breathing resources inevitable for operating in this human-unfriendly environment. The following lines deal with an unexpected discovery revealed by speleodivers in a geologically extraordinary cave. Instead of being located in speleologically famous countries like Venezuela, Vietnam, China or Mexico, the cave surprisingly lies in ... the Czech Republic. If you are interested in exploration of not only the outer space but also the planet Earth's deep underground, then you are at the right place now. Read further about the spectacular recent discovery which will yet continue in the following years, perhaps beating the current world depth record (for the latest July 2017 update [video included] see the end of the article).