Most of these "historic" structures (many of which I've visited) have been standing for 300 years or less. Heck, the most of them date back to the 1800s. This is the norm in eastern nations. In western Europe, the norm is 600 years or more. Many older buildings in Europe were built after 1650, when the Catholic Church banned construction using stone from before the time of Christ. Before then, builders used wood, which gets weathered and worn over time to reveal its age. In fact, outside of England, France, and Italy, almost all buildings are made of wood. Inside cities, buildings are usually made of brick or stone. But even these structures will be covered with paint or plaster if they aren't protected by law. The word "museum" comes from Latin musumum, meaning "a place where trophies are kept." Before the modern era, buildings were used as shelters for people to keep their possessions safe from harm and the elements. These collections of belongings became known as "trophy houses," or "museums." Many museums only accept items that are at least 100 years old as antiques.