According to the International Council of Museums, a museum is a "permanent institution in the service of society and of its development, open to the public, which acquires, conserves, researches, communicates and exhibits, for the purposes of study, education, employment, the tangible and intangible evidence of people and their environment." Museums conserve and showcase a variety of subjects, including history, art, science, and natural history. Art museums tend to preserve paintings, sculptures, and other forms of visual art while other museums focus exclusively on subjects such as a particular type of sports or music. Although most museums are quiet large and are maintained in one building or premises, there are museums that travel to different locations in order to exhibit to the public. Also, exhibitions can be viewed via the internet at virtual museums.