The song is called Peruvian Skies, it's from Dream Theater's 1997 album Falling Into Infinity.
DT is *the* prog/art metal band. They're known for hard, extremely complex and epic compositions. The band formed when three guys met at the Berklee School of Music while studying classical composition.
They kind of have a reputation for being extraordinarily gifted musicians and playing horribly complex pieces just to exhibit their virtuosity with their instruments, not necessarily for writing great songs. Of course, that's not to say they don't have some really killer tunes. You'll get the most out of their music if you've ever studied music or music theory.
If you like the song, you should definitely check out more of their stuff.. I'd suggest starting with their most accessable album, Images and Words. There are a couple of 9-11 minute songs on the album, but nothing like some of their other ones. A Change of Seasons starts with a massive 23 minute 7-parter, and finishes with a jaw-dropping 10 minute jam sequence where the band covers Pink Floyd, Kansas, Queen, Journey, the Dixie Dregs, and Genesis without missing a single beat.
If you want something even more bizarre and experimental in the prog/art rock genre, a few DT members joined up with a couple other excellent musicians to record The Liquid Tension Experiment (1 and 2). The whole CD is incredible musicians doing incredible musician stuff.. nothing that's going to appeal to most people.
