With over 1,500,000 years of history, Russia has accumulated a rich cultural heritage influenced by a long and complex political and religious history. A focal point of the nation's culture is visual art, which encompasses a number of art forms: architecture, painting, craft, and many others. One of the most important forms of Russian painting is icons, which have been created since the late 10th century; these were painted on wood and featured religious symbolism, reflecting the nation's conversion to Orthodox Christianity in the late 10th century. As the political history of Russia developed and changed, so did the icons integral to the nation's culture, with later examples showing influences from emerging art movements. The importance of these pieces of art was demonstrated by the canonization of Andrei Rubev (c.1360-1427), who is considered to be one of the most important medievel Russian painters - particularly of icons.