In the Sanska era, cities in the world experienced a rapid decline in population, as more and more people began to move to the rural parts of the world to escape easily transmitted diseases, which were rampant at the time. Also people began to find negative effects of a city, and also the natural disasters occuring at the time. The sharpest decline experienced was that of Beijing in the People's Republic of Northern China, where ten million residents escaped to the countryside areas.