Bolivia's Salar de Uyuni is a dried-up ancient lake covered by a crust of salt about 10,000 km² in size. Across that whole surface, elevation varies by less than a metre, making it one of the flattest places on Earth. Scientists use it to calibrate satellite altimeters, and after rain it turns into a gigantic mirror.
On 27 August 1883, the eruption of the Indonesian volcano Krakatoa was heard as far away as Rodrigues Island, nearly 4,800 km away. Its pressure wave was picked up by barometers worldwide and circled the globe several times. The tsunamis that followed killed more than 36,000 people.
The deepest known point in the ocean, Challenger Deep, lies roughly 10,900 m below the Pacific surface. Drop Everest in and its summit would still sit about 2 km underwater. Down there, the pressure is more than 1,000 times what you feel at sea level, roughly a tonne pressing on every square centimetre.