I just returned from a very pleasant several-day visit to Tucson, at the invitation of Stephen Kobourov, to visit him and Alon Efrat. I spoke Wednesday morning about xyz graphs; my talk slides are here.

Wednesday afternoon, we visited the Sonora Desert Museum, and then took a short (one hour) hike into Saguaro National Park, where Stephen showed me some petroglyphs at a site he knew of. We had been planning to do this Sunday, but it rained that day, after which the weather was beautiful. Photos here and here.


None: Antigravity illusion
A friend of mine has a lamp shade with very thin disks made of mother of pearl dangling down randomly. Geometrically it looks exactly like the plant in your first picture turned upside down. So it seems to me that the gravity in that desert is directed wrong way and the plant should sound really nice when it's windy there. :)