The world's tallest rollercoaster is here in New Jersey. This is a kind of record that isn't terribly hard to imagine being broken, as it just requires a designer willing to build a structure more than 46 storeys in the air and the financial backing to construct it. But has anyone considered going in the other direction and building the world's deepest rollercoaster? There are so many abandoned mine shafts around the country that there must be one which can be rehabilitated and adapted for the purpose. Could one go fifty meters down, a hundred, a few kilometers deep? Also, to most people, even the rational ones, mineshafts are inherently creepy, especially for the significant number of people with claustrophobia. I am confident that engineers could address the issues of tainted air, of rescue shafts, of inundation, and of evil cave trolls so that such a structure could take over the title of MOST DANGEROUS ROLLERCOASTER IN THE WORLD which would be certain to pack them in.
Of course when one considers technical difficulties, it is well to remember that one is comparing things to the difficulty of building a structure 150 meters up, which is no picnic either. At least you wouldn't have to worry about wind load, rain and snow.
I propose that we turn the problem over to the experts: high-school students.