The ubiquitous circle = city will instantly be recognized, but if not offset by other decoration and ornamentation will look boring. Consider an old-style or pictorial representation instead.
Make your map interesting by including side-view profiles of famous spots such as lighthouses. They are instantly recognizable and will add a great deal of connection with viewers.
This can be really effective in a pictorial city representation!
Here are some symbols from his book Principles of Cartography
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