The tallest is Tokyo Metropolitan Main Building No. 1, built to resemble both a computer chip and a gothic cathedral. It splits at level 33 into two twin towers which stretch to a height 48 stories, making it the tallest building in the city for many years.
Both towers have observation decks free to the public on level 45, 202 meters high. On really clear days, you might even spot Mt Fuji to the west. The view from the southern tower is considered slightly better but the northern tower remains open later, making it more suitable for night viewing.