The atmosphere that surrounds our planet is generally a good thing, everyone agrees. Besides providing air for us to breathe, is also protects us from potentially damaging radiation from space. The ozone layer, for instance, protects us from the ultraviolet rays of the sun. When it comes to observing space, though, the atmosphere becomes a problem. The history of astronomical observatories is partly the history of trying to eliminate the difficulties of seeing through the atmosphere.
Scientists using optical telescopes have two main obstacles to overcome.
This effect is familiar to anyone who's ever compared the number of stars visible in the country to the number of stars visible in the city. The lack of environmental light in a less-inhabited area makes it possible to see vastly more heavenly objects in the night sky. This is partly why most observatories with optical telescopes are located out in the country, usually on top of a mountain. That way, even the lights that might happen to be around will be below the observatory, where they won't interfere. Observatories can be found in remote areas all over the world, from the outback of New Zealand to the desert peaks of Uzbekistan.