General Sherman: World's Largest (not Tallest) Tree
Sequoia National Park, California
The General Sherman owes its record-setting largeness not to its height or girth, but to bulking up better and faster than any other 2,500-year-old tree. A low wood fence has been built between tourists and the General Sherman trunk, so that people can no longer stand right up next to it. However, an accessible concrete "footprint" of its trunk circumference has been added as a photo-op.
Despite its superior size, General Sherman is not as dramatically photogenic as the nearby General Grant tree -- but if you've come this far you really have to see both.