We decided to start the day with a helicopter tour over the Canyon. Just like you can't appreciate the Canyon via photos, it's also hard without seeing it by air.
We spent some more time exploring the area (including DH going to a free talk on Vultures), before heading off towards Hoover Dam. Like the Snowy Mountain River Scheme, I doubt the Hoover Dam would be built in these times, due to the high human cost, but like the Snowy it is a key water source to the area.
Helicopter tour over the Canyon. We did the North Canyon Papillion Tour.
Mule trip of the Grand Canyon. I've always wanted to do this and am still kicking myself for not doing it.
Self tour around Hoover Dam. You can also do a variety of organised tours.