3 of my ex-students bought a "new" Joker Trike 912/ Aeros Profi TL wing together. Its flying a little different than my trike - their "school" trike. Then we did retraining. Joker has a foot throttle (my trike has the hand throttle), Joker has a lower seat than my trike and its faster.
The Mir diamond mine in Siberia is the deepest ‘proper’ man-made hole. It’s 525m deep and 1,200m across. There’s a no-fly zone above it because the downdraft created by the hole had caused several helicopters to crash.