Kingda Ka at Six Flags Great Adventure is currently the "world's tallest and fastest steel roller coaster". Costing a hefty $25-million to build, it goes from 0-128mph in just 3.5-seconds (1.67g's) -- powered by a 20800 horsepower hydraulic launch motor -- and the steel track peaks at a daunting 456-feet. Click here for more pictures. Video after the break.
