Some of the earliest photographs of old Beijing are set to go up for sale in London on Tuesday. Shot more than 150 years ago, the 18 pictures reveal a Chinese capital long since gone. At the time, they were the first images of China most Europeans had ever seen.When they come up for auction at Sotheby's, it's believed bidders from around the world -- and in particular China -- will value the pictures at around half a million dollars. The price tag on these photographs a reflection of their unique nature.