Cologne is a city in the state of North Rhine in western Germany, with a population of nearly one million, making it the fourth largest German city in terms of population. Cologne is one of the largest educational centers in western Germany, as it has the University of Cologne, as well as many educational and research centers. It is also one of the country's political centers as the Federal Government Office for the Protection of the Constitution is located. The city extends over a distance of 405 km, and contains vast green areas. The parts within the city limits have been converted into public parks. As for the parts outside the city, they are economically exploited forests. In addition, Cologne has about 22 nature reserves that shelter rare animals and plants. There are many amazing historical monuments in this city, as it has been settled throughout history by many ancient civilizations and empires, and among these monuments you will find the Roman Cologne Cathedral, which is one of the landmarks that has been included in the UNESCO World Heritage List.