The Undying Lands are a mythical and unique place within the realms of Middle-earth that are only accessible to Frodo and Bilbo for a special reason.

The Undying Lands are an important location to The Lord Of The Rings, though only a few individuals were ever able to enter.

Samwise Gamgee journeys to the Undying Lands after The Lord of the Rings, and there's a specific exception that allows him to be there.