Access to Hell's Half Acre South side of highway. Hell's Half Acre - This unique setting of natural beauty covers approximately 320 acres. Investigation has confirmed that in former days the Indians drove great herds of buffalo into this depression for slaughter. Flint arrowheads and buffalo bones have been found here. A detachment of Captain B.L.E. Bonneyvill's party visited this site in July 1833. With half of the earth’s geothermal features, Yellowstone holds the planet’s most diverse and intact collection of geysers, hot springs, mudpots, and fumaroles. Its more than 300 geysers make up two thirds of all those found on earth.