The Tokyo Metropolitan Government Building serves as the city hall for all the wards and cities that constitute Tokyo. The building is located in Shinjuku in front of the Shinjuku central park. The main building is composed of two columns that are structurally linked up to about 2/3 of the height of the whole tower. Above that height, the two structures rise separately towards the sky. The top floor of each of the two towers host an observation deck that is free of change. They are accessed from two separate elevators located in the basement floor.
On a clear day, one can see many landmarks of Tokyo from the top, including Tokyo Tower, Tokyo Skytree and Mount Fuji. I recommend visiting the tower before its closing time of 6:45PM and then head to Shinjuku and Kabukicho to enjoy their vibrant nightlife.