Real Giant trees a la Avatar

Hi there,

I was watching this show on H2 (history 2?) channel about World War 2 battles, and this particular episode was about Guadalcanal.

So they managed to recreate a 3D map of the island based on aerial recon maps of that time.

What struck me was the existence of giant trees (they looked like mushrooms from above) which was right out of Avatar!

Anyone know what these trees are called? And where else do giant trees exist, outside of California?