We should be clear: there is a difference between "gravity waves" and "gravity." Gravitational waves are the (still) theoretical radiation caused by accelerating mass, similar to electromagnetic radiation being caused by accelerating charge.

The current tool for detecting GWs is the LIGO system. It consists of three interferometers, two large in Hanford, WA and Livingstone, LA, and a half-size built near the Hanford full-size. The interferometers are an amazing sight... the arms are several kilometers long, each. They are so long, in fact, that in order for the light-paths within to be perfectly straight, the arms do lay directly on top of the ground, since the earth's curvature would have a slight effect on the path. (I worked in a research group that analyzed data for characterizing the interferometers, so I may have used too much tech-speak, sorry).

For more information, go to this website.