What the Beatles were to the '60s, Led Zeppelin were to the '70s: a band so successful and innovative they wound up creating the prism through which their entire epoch was seen. Zeppelin ushered in the era of album rock -- they refused to release singles off their albums, even when they were garnering massive radio play -- and of arena rock, playing ever-larger stadiums as their ticket sales skyrocketed. Other bands played on a similar field but Led Zeppelin carried a unique mystique cultivated by cryptic album art, distance from the press, and, of course, their music.