There are many famous sightseeing spots in Japan. When talking about sightseeing' in this article, it will be defined as "places that tourists and other visitors to Japan may find interesting".
There are several different types of sightseeing locations or tourist attractions in Japan. Some people visit Japan because of the ancient culture, some visit because of the high tech elements, some visit for nature, others visit to hit the famous bars and nightclubs in Tokyo. In fact, there are so many different places that people may find interesting in Japan that listing all of them would be almost impossible. The best way to list sightseeing areas of Japan may be to break them down into categories.
Some people come to Japan to visit the city centers of Tokyo and Osaka, including the shopping and Japanese nightlife hot spots like Shinjuku, Shibuya, and Harajuku. Still others might be interested in Akihabara and all of the computers, robots, anime, manga, and high tech gadgets that it entails.
Some people come to Japan to visit Kyoto, Meiji Jingumae Shrine, the ancient mountain top retreat of Koyasan, Tokyo Castle, the ancient ruins scattered throughout Okinawa, and to watch the centuries old sport of Sumo. There are many other places and things related to "old Japan".
Some people come to Japan with an interest in action sports like snow skiing in Hokkaido or Yuzawa, surfing along the Japanese coast in areas like Enoshima and Kamakura, or rock climbing one of Japan's peaks.