definition
strict definition
observation area closes permanently
A room or deck for high observation is closed to the public, without prospect for re-opening.
An observation area closes permanently when access is shut off to the general public without any scheduled re-opening. This may happen for various reasons, such as impending demolition, vacancy of the whole structure, or because the observation area is no longer economically viable.
This may apply to either an indoor observation floor, an outdoor observation deck, or an area combining both of these.
The event concerns the end of general public access without a scheduled reopening. A temporary closure with a reopening planned is distinct; the observation space can remain physically intact after permanent closure.