In the Voyager episode ' Relativity', we actually get a wide shot of the Utopia Planitia Fleet Yards as a whole. You can see through the window a shot of a Galaxy class ship under construction in what appears to be an expansive and enclosed space compared to the typical spacedock we've seen in other episodes and films. Here's Geordi LaForge during the TNG episode ' Booby Trap' where he creates a holographic representation of Utopia Planitia and his girlfriend the Galaxy class designer Leah Brahms. There are some different perspectives in The Next Generation and Voyager where the fleet yard appears on screen.
It's not explicitly a starbase, but otherwise appears to meet your criteria and does contain structures that would commonly be called a starbase in that it's a large installation in space. Utopia Planitia Fleet Yards is a dedicated fleet yard in orbit around Mars.
