The Black Hole at Alton Towers back in 90's - A fully covered (and fairly small) roller-coaster which, being covered, meant it was pitch black inside so you never knew where the track was going and what direction was next so you got thrown around a huge amount, smashing your knees to bits or being squashed to death as it was tandem seating (one behind the next) in each cart, with just a lap belt to hold you in
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en.wikipedia.org
As it was -
Uncovered during its build so you can see the layout (which you couldn't once it opened) -
The carts, friken lethal things!!!!!