My first thought was to take a picture of the bark of one of our Live Oaks pointing up from below so that the rest of the tree is in the frame as well. Later I realized that I'd already done this before - in Trivandrum in 2006, under the Nagalinga tree.

Most of you from Madras or the South of India know this tree and must have seen it before. For those who haven't - this flower is called Nagalinga because the pink flower looks like a serpent head (Naga) hovering over a linga.

The flowers smell heavenly and at the peak of summer when all the flowers are in full bloom, you can find this tree just from its fragrance, from several meters away.
There was one tree in some private land across the street from where we lived in Madras. So though I could see them, I couldn't ever get close enough to the flowers. Then when I was in Trivandrum with my parents in 2006, we found this tree within the Shastha Temple grounds! It was in full bloom and I got some good pictures.
When I looked online for details about this tree, I couldn't find too much info. There is one blog entry in someone's blog that describes the Nagalinga Pushpa, but that's about it.
When I searched for Cannonball Flower however, I found many more links.