They seem to be the rage now. San Francisco, being full of the smartest, most progressive folk I've ever encountered, is building the world's greenest skyscraper as the centerpiece of the massively huge Transbay Terminal project that will connect SF to LA via high-speed rail trains (like France's TGV but faster and quieter). Think Grand Central Station but 50 times more advanced - and sleek and sexy like something out of a futuristic sci-fi book.
This is one of three designs submitted for consideration. These are my favorite pics from SOM (Skidmore, Owings and Merrill). (Via Inhabitat).
Here are some pics: