This document summarizes how Beijing has changed over time due to a variety of influences. It discusses how the air quality has worsened due to increased pollution from factories, vehicles, and population growth. It also describes new sports facilities like the Bird's Nest and Water Cube built for the 2008 Olympics, as well as the destruction of traditional hutong neighborhoods to make way for new development. Additionally, it notes how foreign investment since the 1970s has increased jobs and status symbols, leading to high population growth and making Beijing one of the most crowded cities in the world.