My next 1970 album is Led Zeppelin III
This is my favorite Zeppelin album by far, from the hard rock on side one to the quiet acoustic folky stuff on side two to the shout out to Roy Harper at the end. It's like the lost gem of their catalog, especially if you include "Hey Hey, What Can I Do", Led Zeppelin's only bona fide rarity.
Here's the famous viking kitties video for the A side of that single. This comes from 2005, before youtube or even LOLcats! It's hard to find a version with both the audio and the flash animation.
I like "Immigrant Song" because it's the shortest Led Zeppelin song in my iTunes library (which doesn't have all their songs). Just two minutes and twenty five seconds!