A Zoo is a closed area, where animals are grown, and are kept within a closed circuit of either cages, or within a wide spread area, but split by a safe distance from the public. National parks are also zoos, which are very large in size ranging from approximately a few 100 square kilometers to a few thousand square kilometers. The Northeast Greenland National Park in Greenland, is the biggest national park of size around 972,000 square kilometers. National parks do not have a physical boundary. National parks are typical dense forests, where animals are protected in their own home place, and public are allowed to view animals at selected places in the forests.