Thanks, Penolta, for giving some additional facts. There's a Sequoia in the Mariposa Grove, Yosemite National Park, that's completely hollow but still alive. I think they call it the chimney tree - you can actually stand inside it and look up to the living crown. The tree was hit by lightning at some point (lightning fires are common in the Sierras) and burned inside. The layer along the bark (which is actually rather soft and spongy feeling) that transports nutrients and keeps the tree alive wasn't damaged. It's only been in relatively recent years that scientists have convinced those who tend the wild lands, that fire is not always an enemy, and sometimes necessary for the health of a forest.
I did take a couple of pictures of their tiny cones, but was rushed and they weren't very good. I'll have to think of a creative way of showing how small they really are, compared to how huge the trees are.