On my recent visit to Newark I popped in to the Tourist Information Centre where they recommended I visit the Town Hall Museum. It’s certainly housed within an impressive building; built in 1776 it is Grade I listed and the museum opened up in part of the building in 1999. Entry was free, though unfortunately photography was not allowed inside.
The Museum is actually quite small (apparently there are other artefacts to see on a different floor to the main museum but that didn’t seem to be accessible when I was there) but it did have some lovely items, including the traditional robes worn by the Mayor on ceremonial occasions.
The Spotlight Gallery was hosting some really fantastic recent paintings by local artists and there was also much artwork and sculpture by 20th century artists who had a connection to the area.
I’m not necessarily sure I would recommend a visit unless you had a few minutes to kill as it didn’t seem particularly extensive but at least it was free and easily accessible.