The Arctic Building, completed in 1917, is unique for its intricate terra-cotta ornamentation and 25 walrus heads peeking off the building’s exterior. Though the walruses’ tusks were originally authentic ivory, an earthquake in the 1940s managed to shake a few of them loose to the ground. To protect passersby from the unusual urban hazard of being skewered by falling tusks, the ivory was replaced with epoxy.