TIL that horses have no muscles in their lower legs, so their hooves act as "second hearts". A horse that can't move risks blood pooling in its hooves, which can cause tissue death starting from the hooves up. This is a key reason why leg injuries are often fatal for horses.
TIL during WWII, Britain hid its wealth 3 floors under Montreal's Sun Life building. The vault had microphone alarms, walls made of abandoned railway steel, and a door needing 2 blind, simultaneous codes. 120 secret workers sorted billions under strict oaths to keep the entire operation hidden.
TIL that the Ojibwe language, spoken across the Great Lakes region, has no gendered nouns like many Romance or Germanic languages. Instead it categorizes nouns as animate (tree, feather) or inanimate (river, heart).