How can I find tall buildings with a publicly accessible view at an upper floor?

Many travelers enjoy great views from high vantage points such as a hill nearby a city (e.g. Mount Monserrate in Bogota, Colombia), or the (less popular than the Space Needle, but taller) Columbia Center in Seattle. How can these places be found?

For geographical features such as hills or mountains near a city, a topographical map could be consulted, yet there's no guarantee that points at high altitude are accessible at all, thus making the process painful. For tall buildings, top attractions on TripAdvisor, LonelyPlanet or the like can be helpful, yet one still needs to manually figure out if the attraction is likely to have a high vantage point.

What are some better ways of figuring out places from which a traveler can take in sweeping views of an entire city? Observation decks, restaurants, cafes, anything that's perched high up.