This 37 foot (11 m) tall towering rock of travertine limestone was deposited by a hot spring active in one location for a long time but is now extinct. The Cap has been greeting visitors to Yellowstone National Park before the Park's creation in 1872. It received its name before the Park was even created and is supposedly named for the conical hats given to emancipated Roman slaves later worn during the French Revolution. Sediment has spread out into a flat area from its center at the front springs. The internal pressure was adequate to raise the water to a considerable height which allowed a continuous slower building of mineral deposits for possibly hundreds of years. This natural volcanic landform is just a stop off the Grand Loop Road. You can walk the boards to view the lower terraces and the Liberty Cap. Stop off the Grand Loop Road and tread the boards viewing the lower decks and the Liberty Cap. The Terraces are active, but you'll have to climb the stairs to get to the top.