A Victorian gentleman hopes to find his long-lost son, who vanished whilst searching for a mysterious Viking community in a volcanic valley somewhere in uncharted Arctic regions. The gentleman puts together an expedition team to go on the search, but when they reach their destination they must escape from some Viking descendants who will kill to keep their existence a secret.
See also: Lost Horizon (1937 and 1973)
Jan Lamprecht - Hollow Planets
Journey To The Hollow Earth