Richard Byrd, a highly decorated US Naval officer whose supposedly hushed-up “secret diary” of a 1947 expedition to the North Pole is believed to contain descriptions of a land full of lush lakes, greenery and woolly mammoths

Have you ever read 'Journey to the Centre of the Earth'? Sounds mighty familiar... lol... I'll keep reading...

(Byrd was actually in the South Pole at the time)

After a long analysis, this website concludes:

ence the various grains of truth pertaining to Byrd’s historic operations have seeded themselves in the fertile grounds of myth an speculation, taking on a wholly new–and utterly fascinating–life of their own in the years that followed.

And I wanted to be fair so this website describes itself as ' We attempt to explore the mysteries of our existence by relying on scientific knowledge, and without catering to unfair or cynical criticism.'

So even a website open minded enough to entertain the idea concludes it's mythical at best. You can read more here:

http://www.gralienreport.com/ufos/the-odd-exploits-of-admiral-byrd-bitter-reality-at-earths-end/

Sometimes we need to be aware that just because things make sense, or things fit with what we want to believe, it doesn't make it true. There are numerous wild conflicting versions of this story and zero evidence to back it up, unfortunately. Though it makes a fantastic read by Jules Verne!