From the Super Mario Wiki
Vista Hill is a large hill that is connected by a long bridge to Bowser's Keep. However, during the events of Super Mario RPG: Legend of the Seven Stars, the gigantic sword Exor destroyed the bridge, preventing any access to the castle by land. Currently, the hill can only be used to gaze at the isolated keep. Mario's Pad is to the east of Vista Hill.
There is an area in Mario & Luigi: Bowser's Inside Story that also allows a view of Bowser's castle from a distance. It is not referred to by name, however.
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