The "Solarium" was not a place of relaxation. In the show’s lore, it was a top-secret government installation located beneath the ruins of a 14th-century castle in South Bohemia. Episode 13—the final, never-officially-aired installment—supposedly documented a catastrophic failure of the facility’s radiation shields during a "chromotherapy session," resulting in the slow, grotesque mutation of the inhabitants.

A solarium is designed for healing: light therapy, vitamin D, warmth. In the show’s fictional universe, the Czech government weaponized this. They built —a "quantum solarium" that used concentrated radiation to "erase undesirable memories" from dissidents.

Whether that is truth or a continuation of the legend is for you to decide.

It succeeds because of its specificity. "Czech" grounds it in a real, gritty history. "Solarium" provides a mundane, almost boring setting. "13" promises a climax. Together, they form a keyword that feels like a secret handshake.

three former employees of the Jáchymov sanatorium (which is a real location, now a museum) have anonymously stated that Basement Level 3 is "permanently sealed with concrete" and that "guides do not take visitors there after 1:00 PM."