Did you know? Grand central station produces more radiation than allowed in a nuclear power plant. Grand Central Station gives you a dose of radiation when you go through it, thanks to the granite used to build it.
Well, radiation is a part of the natural world, and so things made with natural materials often contain radioactive elements. In the case of Grand Central Station, the natural material is granite. All natural rocks contain traces of radioactive elements, but granite contains more than others, and certain specimens of granite contain especially high concentrations.
It's worth noting that if Grand Central Station were a nuclear power plant, it would be shut down for exceeding the maximum allowable annual dose of radiation for employees. That being said, it's not actually a dangerous place. You can enjoy all that beauty in every inch of the terminal relaxed and amazed.