From the late nineteenth century until the end of the Second World War Porthcurno played a pivotal role in the history of global telecommunications. Porthcurno became internationally famous with the laying of the first submarine telegraph cables, the first to Carcavelos in Portugal in 1870, followed by locations all over the globe. The station was originally run by the Eastern Telegraph Company which later merged with Marconi's Wireless Telegraph Company and then became Cable and Wireless.

Because of Porthcurno's importance to wartime communications and its vulnerability to enemy attack in 1940 local tin miners worked to bore a tunnel into the granite hillside and the station relocated underground. There are actually two connected tunnels. The main entrance was protected by double bomb and gas-proof doors and at the rear an escape tunnel lead to the hill-top above.

Porthcurno ceased operation in 1970 exactly 100 years after the first cable was laid, and shortly after re-opened as a museum. The exhibits are located in the tunnels, the Instrument room, Cable testing room and Workshop occupy the North tunnel and the Showcases are in the south tunnel which also accommodates a Maritime room and demonstration area.