Raumschach (German for Space Chess) is one of the first three-dimensional chess variants and the first to survive until present times. It was invented by Herr Doktor Ferdinand Maack in 1907. Maack first experimented with an 8x8x8 array but later determined that a 5x5x5 array yields a nicer game. Maack founded a Raumschach club in Hamburg in 1919, which remained active until the Second World War.
Rules for Raumschach:
Raumschach: the Thoroddsen board