A hall is what you call a spelled piece of space-magic that's open for the public.

A tower hall is a hall that was part of the original design of that particular Tower, and retains the Tower's ancient architecture design. Tower halls are considered to be cultural heritage sites, and are usually at the heart of every Tower's richest and most influential residents.

Examples of halls could be a bar, an arena or a garden. A hall is not the same thing as a realm, which is much larger. A hall can, but usually doesn't, contain a horizon sphere.