Sweden: Grimeton Radio Station
Grimeton Radio Station is a historic radio station that was using the longwave (17,442 meter was the wave length) transatlantic radio telegraphy to communicate with similar stations across the Atlantic in the beginning of the 20th century – from 1922 until 1940 – sending Morse code encoded messages. Since 2004, it is a UNESCO World Heritage site for being the only remaining example of an early pre-electronic radio transmitter technology known as Alexanderson Alternator. The technology required similar large stations across the globe to send and receive brief Morse code messages and became obsolete in the mid 1920s. Nevertheless, the station operated during WWII and Nazi occupation. Today, the side has the remaining equipment and the associated museum.
