Murals in Northern Ireland have become symbols of Northern Ireland, depicting the region's past and present political and religious divisions. Belfast and Derry contain arguably the most famous political murals in Europe. It is believed that almost 2,000 murals have been documented since the 1970s. In 2014, the book, The Belfast Mural Guide estimated that, in Belfast, there were approximately 300 quality murals on display, with many more in varying degrees of age and decay. Murals commemorate, communicate and display aspects of culture and history. The themes of murals often reflect what is important to a particular community. A mural therefore exists to express an idea or message and could generally be seen as reflecting values held dear to that community.