There's more photos of petra on my flickr account (see left "suggested visitations").
I went to Jordan for a day while I was in israel. It was like being inside an antiquity, with no strings attached. 95% of Petra is still unexcavated, or so they claim. My tour guide, Hussein, seemed more interested in making jokes to the tour group while the old caught their breath from walking, than in telling us everything he knew about the town.
What I've ascertained are some basics: Petra was a very important, and defensible, stop on the spice trade routes. They loved (and we still love) their camels. The treasury was not a treasury, but a funeral tomb. Most of the carved rooms in the cliffs were. The rocks tumbling down all the hills were the bricks cut out of the cliffs while making the funerary tombs, these stones at some point were built into houses for the people who were eventually buried in the cliff sides. An old roman road runs through the center of town, with some ancient trees and the ruins of a temple, and some other buildings. This road was the main drag, with booths and shops and all the glorious commerce you'd expect from a roman-conquered town.
If you enter the city through the same route as indiana jones, you'll see a water trough carved about waist high in the walls beside you, and walk straight into the most stunning view of the treasury- the prettiest graveyard in the middle east. (Egypt might argue on that, but they're in africa, and I haven't been there yet.)
But the cliffs, when you climb away from the ill-informed tour group, and away from the snapping german tourists, the cliffs are quiet and resonant all at once. The ground is covered in boulders streaked with undulating layers of ancient silt, and shards of greek pottery still power the dirt. The red is from the iron, not the pottery, but is so strong that it blinds itself from your eyes, and you see ribbons of yellow and white and blue in the rock. If you pocket a few stones like I did, hoping to bring home a reminder that petra isn't jus red, you'll find the starkly different colors you saw there are shades of red when your eyes readjust to the rest of your life.
The colors of Petra are about extreme subtlety and quiet. They are the underlying resistance of the beaudoins who were pushed from these caves, and the spice traders who were forced to abandon them. The stones from my pockets left a dust in my suitcase that scared the israeli airport security. I'll leave them on my father's grave next week. All the places in the world he never got to, I'll just bring a little bit back.