Tokyo Station’s iconic red-brick Marunouchi Station Building is the subject of the 5th postcard in the Tokyo series. This beautiful building was recently restored to its former 1914 glory in 2012, after being damaged greatly by the bombing of Tokyo in WWII in 1945. At that time, the domes were shattered among other damage, and the temporary square roofs became permanent over the years. The renovations took about 5 years, and the Yaesu entrance on the other side of the station is still being renovated. You can read more about it at wikipedia here.
Tokyo station is the busiest in Japan, and because the renovation is still very recent, it is not uncommon to see huge hoards of people photographing the building. As the main station in Tokyo with connections to both airports as well as Shinkansen lines stretching across the country, it is an easy station to visit for tourists and locals alike!
You can read more about what to do and see around this station at Japan Guide here.