A cat tree (also referre to as a cat condo) is an artificial structure for a cat to play, exercise and relax on. Cat trees vary in height with cats preferring ones that are tall enough to allow them to see everything in their environment. Cat trees are usually constructed of wood and then covered with carpet or a similar fabric that encourages and allows a cat to scratch. Cat trees are often used specifically to prevent scratching of other household items. In addition to carpet, trees may contain other desirable items to encourage scratching of the tree such as sisal rope, and cat toys.