Mordor or anything like that.
"The Wizard of Oz"
Not only one of the best quest movies ever made, this is also one of the most famous movies to ever come out of Hollywood, period. Everybody knows the story: Dorothy's house gets picked up by a tornado and dropped into the land of Oz (and on top of a wicked witch, provoking the sister of whom to swear revenge) where she encounters all kinds of weird creatures in her quest to return home. There's also music!
"The Thief of Bagdad"
Think of this as the hipster douchebag's answer to "The Wizard of Oz." The special effects are even better, and you've got a bonafide auteur, Michael Powell, behind the camera. The quest itself is being undertaken by one King Ahmad, who has to join up with a thief (played by famous child actor Sabu) in order to regain his throne and his girl. There's also a flying horse in this cult classic!
"Jason and the Argonauts"
Jason's quest to find the Golden Fleece is one of the oldest stories in the world, but it was never told better than in this 1963 classic, thanks to the special effects from stop-motion animation genius Ray Harryhausen. Jason teams up with a lot of guys, most notably Hercules, and runs into a lot of monsters, most notably giant statue Talos, in his quest for the Golden Fleece. This must be one hell of a fleece. There's also a bunch of skeletons!
"The 7th Voyage of Sinbad"
Another film from Ray Harryhausen, this one featuring the famous Sinbad the Sailor, who runs afoul of some wizard and has to find the magic lamp in order to restore his girlfriend to her proper size. To do it he has to fight a skeleton, a giant cyclops, and some other beautifully animated bad guys. There's also a child genie!
"Monty Python and The Holy Grail"
One of the most famous quests in all of history is that of the Holy Grail, the Holy Grail of Holy Grails. In Monty Python's batshit (and highly influential) comedy about that quest, everything from killer rabbits to the existence of God and the capacity of a swallow to carry a coconut are covered, and it's undoubtedly one of the funniest movies ever made, quest or otherwise. There's also a "string of pussy jokes"!
"The Lord of the Rings"
loooooong time to finish. Peter Jackson took this to heart when he told the story of Frodo Baggins and his quest to destroy the One Ring in the fires of Mordor. He took three movies, each at around three hours in length to tell the whole story. That's, like, nine hours right there, not even counting the credits. There's also a dwarf!
"The Holy Mountain"
Not all quest movies are family-friendly entertainments. This film from surrealist Alexandro Jodorowsky has a Christ-figure (played by the director himself, of course) wandering through all kinds of bizarre settings, including a guy cutting off his fingers and a bunch of naked boys. Like we said, this isn't one for the whole family to watch once a year on ABC. There's also drugs!