Although Yellowstone National Park is renowned for its multicoloured hot springs, impressive geysers and legendary Grand Canyon, it also provides an important refuge for wildlife. This vast wilderness is one of the last remaining strongholds of the grizzly bear and in recent years wolves have been reintroduced into its ecosystem. While Old Faithful can be counted on to erupt at regular intervals, visitors' chance encounters with the park's large mammals will make an even more lasting impression on them.