It is currently not possible to set that no bookings for “external visitors” are allowed at a location/area. So that only internal colleagues can book, e.g. for themselves or for an internal colleague, but not for external visitors.

Yes, there is a setting under Advanced settings>Global settings
Under the “Personal space” tab, there is a setting “Allow personal spaces to be booked for external users” where you need to disable the checkbox.

However, if this setting is disabled, it will be disabled globally for all locations. We would need the option to disable this setting for a single location.