Well, to me its all one canyon. Grand Canyon begins where the Little Colorado River meets the Colorado River. Upstream from that is what is called Marble Canyon which begins at Lees Ferry, Arizona. Upstream from that is Glen Canyon. 15 miles of it are still there, the rest - upstream from Glen Canyon Dam is sadly under water - under what's now called Lake Powell.

I shot the pic from the bridge just downstream from the dam so that's the upper end of Glen Canyon in the pic. If you were on the water you'd go downstream to Marble Canyon then the Grand Canyon then Lake Mead behind Hoover Dam.