Mount Royal (Mont Royal) is a small mountain in Montreal, immediately west of downtown. It is the site of Mount Royal Park, designed by Frederick Law Olmsted and the city’s largest park.
Above, Mount Royal seen from the observatory of Au Sommet Place Ville-Marie. The Belvédère Kondiaronk, on the left, offers a great view on the city. The Mount Royal Cross can be seen on the right.
The Tour Montparnasse is a 210-meter office tower in Paris. It was the tallest building in France until 2011. Its roof is open to the public and provides a great view on the city.
The Hague Tower (Haagse Toren or Het Strijkijzer) is a 132m tower in The Hague. Its top floor houses an outdoor observatory.
At 131m, Kyoto Tower (京都タワー) is Kyoto’s tallest building. The observatory is at 100m and offers a great view on the city.
Tokyo has many skyscraper observatories open to the public. On a clear day, it is even possible to see Mount Fuji and a good part of Kanto. Here is a list of the ones I have visited so far. I have also made a map to show locations.