From below, Shibuya Sky, the rooftop observatory atop Shibuya's newest tower, Shibuya Scramble Square, looks like one of those harrowing infinity pools – people leaning over the edge of nothingness. Rest-assured, it has plenty of safeguards, but the open-air, 360-degree views from 229m (the tallest in Shibuya) are still awesome. Also there are sofas and hammocks for lounging up here.
The entrance is on the 14th floor, from where an elevator takes you up to the 45th. To avoid queues (and save a few hundred yen) purchase tickets online in advance; you must choose the specific date and time. Note that there is some strobe-effect lighting once your enter. There's an indoor observatory on the 46th floor (open even when the roof is closed for bad weather). Anything that doesn't fit in your pockets needs to be checked into a (free) locker before visiting the roof.