 Something which has always puzzled us at Mystery History, although the mountains of pyramids, the gigantic megaliths, indestructible artifacts, or the out-of-place artifacts, is the massive amount of underground cities found all over our planet. Extraordinary undertakings seemingly necessary at some time in the very distant past. Complex tunnel networks almost telepathically hewn direct to each other. Located from hard bedrocks, with many exhibiting considerable efforts committed into security. Huge rolling doors can be found at many crucial junctions within the underground systems, as can be found, for example, amongst the underground cities of Cappadocia. Derinkuyen particular still exhibits its rolling doors still in situ. No one displaying the builder's impressive capabilities, but also the abilities of the rolling stone operators. As whoever built these contraptions, unarguably still possessed megalithic stone-moving knowledge. Knowledge we hypothesize is lost knowledge, due to the builders of said sites also a lost civilization, which instead of where they have been placed chronologically by funded investigations, actually, we believe, originate an unimaginably longer time ago. As far within an antiquity, not only lost, but actively dismissed. But regardless of the impressive feats these underground cities were to create, the question persists, why? Why go to so much effort? The cities of Uskanakt, Derinkuyu, and Kemakli, all found just within Cappadocia, Turkey, are not only some of the most complete underground dwellings, with Derinkuyu estimated to have once been capable of housing 20,000 people. Derinkuyu even connects to Kemakli via an underground tunnel, an astonishing 8 km long. And this is but a tiny fraction of the ancient underground cities, which have so far been found all over the world with more discovered each day. Many seem to have simply been sealed when no longer needed, thus many still lay undisturbed to this day. Derinkuyu, for example, was only rediscovered when a wall was knocked down in a house during renovation work. All seemingly constructed around the same time, yet any definitive motivations for why ancient man decided upon such drastic efforts worldwide have yet to be substantiated. Their construction remains a complete mystery, a fact we find highly intriguing. Many people will argue that these cities were chiseled by slaves over many years and at great suffering, a safe bet narrative which jives with the mainstream. When it comes to the academically claimed ages and due to the people during said ages substantially lacked any advanced stone cutting technologies imperative for creating such vast works. This argument, however, thanks to the volumes of examples of exquisite, astounding feats discovered as a special few of these underground complexes, not only installed clearly to demonstrate an acoustic level of awareness on par with prodigal ability and possibly many other as yet undicipered features displaying excelled understanding of many of life's most intriguing subjects. The Hypergeum, located within modern-day Malta, is but one of many examples which can be presented as proof that whoever built these underground layers at minimum possessed astonishing acoustic knowledge far ahead of man as well as almost physics-defying stone-moving techniques displayed in the structure itself. The Hypergeum possesses a characteristic designed into its construction which is simply astonishing. It is so mystifying that although very little is known regarding how it was achieved, a certain frequency it can amplify which seems to stimulate the building's amplifying capabilities as if the entire structure resonates and has since been shown to also affect the human brain becoming known as the god frequency. Who built these underground labyrinths? Why? When did they build them? We find these incredible relics of a lost civilization highly compelling.