Monuments are generally located in parks and gardens, squares and intersections, or near public buildings. There are several types; until the 19th century the most common were the column, the triumphal arch and the equestrian statue, three types of monuments inherited from Roman art. Later monuments were busts placed in niches, medallions, fountains, steles and pedestals, friezes, reliefs, commemorative plaques, gravestones, followed by installations, land art and multidisciplinary works. Commonly-used materials include wood, plaster, terracotta and other ceramics, stone, marble, bronze, iron, steel, concrete and aluminium.