atlantis: the lost empire
A 2001 animated film produced by Disney. The story centers around the character Milo Thatch, whose dreams of finding the legendary titular city are realized with the help of an expedition funded by a friend of his late grandfather. His resulting adventure not only leads him to the city, but also to uncover its secrets as well as those of the expedition.
Though a financial failure, the film would develop something of a cult following as the 2000s and 2010s went on. Similarities were also noted by some to the events of Nadia: The Secret of Blue Water that resulted in plagiarism accusations being made, though these never saw the courtroom.