University of California, Berkeley: Ben Waggoner & B.R. Speer's "Introduction to Archaea"
Read this page. Archaea adapt to diverse environments. Many archaea are extremophile, meaning they live in an environment that seems very hostile to the human eye.
Click http://web.archive.org/web/20160623233943/http://www.ucmp.berkeley.edu/archaea/archaea.html link to open resource.