X-Seed 4000: Some great browsing at this buildings site – this is the tallest building in their ‘vision’ section for structures which are never likely to be built. It seems somewhat arbitrary to say that the X-Seed is the tallest building ever designed, though, even with their secret “by a proper architectural firm” caveat. Especially given that the drawing reminds me of those great ‘spaceship’ Top Trumps where poor old Apollo 9 rubbed shoulders with a host of made-up star cruisers (and the Death Star! Except maybe they couldn’t call it that!).