Monuments are generally located in parks and gardens, squares and intersections or near public buildings.[6] They are of several types; until the 19th century the most common were the column, the arch of triumph 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.[7] Materials used are wood, plaster, terracotta, ceramic, stone, marble, bronze, iron, steel, concrete and aluminium.[8]