Displayed to the immediate left of Mural 2, Mural 1 depicts horrifying scenes of death, destruction, extinction, and more. 
Fun stuff. Check out the full-sized version for more details and disturbing weirdness.

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These murals have generated quite a bit of controversy since their installation at the new Denver International Airport (DIA) in 1994. They've been tied to just about every New World Order-related conspiracy theory out there, and it's not hard to see why. There's no immediately apparent cohesion between all four, yet they're filled with terrifying imagery and seem to indirectly promote some kind of globalist message or agenda. Some people say they point toward world socialism as the answer to all problems on earth, while others insist that these are symbolic revelations of what the New World Order folks have planned for us. Some even claim that they've been altered over the years for various untold reasons. Do a Google search, and you'll see how many nutty conspiracies are out there regarding these things.

The artist behind the pieces, Leo Tanguma, had this to say about them: 

"In Peace and Harmony with Nature" addresses environmental issues of the world. One side of the mural shows children pouring out great sadness over the destruction and extinction of life - human, flora and fauna. The other part depicts humanity coming together to rehabilitate and celebrate nature and its diversity.

"The Children of the World Dream of Peace" is a powerful mural expressing the artist's desire to abolish violence in society. One part of the diptych exhibits the tragedy and devastation of war and its impact on humanity. The mural then moves to images of smiling children dressed in folk costumes from around the world celebrating peace prevailing over war."

His website provides more details, and it's quite possible that there's nothing to these beyond what he's explained.

Personally, I have no idea. Considering their size, placement, and creepy weirdness, I do find it somewhat hard to believe that these are merely about promoting peace, environmentalism, and diversity. It really seems like there's more to the story, but nobody seems to know what. There's a lot of symbolism in them, so perhaps one day someone will 'crack the code', so to speak. 
Whatever their underlying message(s), they're certainly creepy to look at as you're on your way into the baggage claim area. Nothing says "Welcome to Denver" like a bunch of 10 foot high murals showing dead kids, burning forests, and Nazi-like soldiers.

Anyway, study these for yourself and leave comments if you notice anything particularly significant or know more about these.