A "condominium" is a form of real estate ownership in which each owner has title to a specific unit or apartment in a project and joint ownership in the common areas of the project. Maintenance fees or condominium dues are paid to the condominium association to maintain, repair, or improve the common areas. Common areas include driveways, roofs, elevators, and swimming pools. Condominium ownership has become more popular over the years, and has become very popular in some US cities such as Las Vegas, Miami, and San Francisco.