Castle in the Sky 1986

An alternate reality set in the early 20th century. A girl named Sita is in possession of the Flying Stone. Government agents and pirates are hunting for it because the Stone is of immense value. While trying to escape her pursuers, Sita meets Pazu, a boy her age who works in a mining town. Together, the children discover that the Stone is the key to the mysterious flying island of Laputa.