In terms of spaceships that appeared on screen (in this case, television), the flagship "Fesarius" commanded by the diminutive Balok (played by then child actor Clint Howard), positively dwarfed the starship Enterprise.  Let's see, the TOS Enterprise is listed as 947 feet long.  The Fesarius kept approaching until its "buckyball" surface completely filled the TV and Kirk's ship stretched only about a third of the screen's width.

I'm gonna pull a number outa' my @$$ and say the Fesarius was probably 5 miles in diameter.  Yes, I know that's nothing compared to the Deathstars, but for its time, it was probably the largest "filmed" vessel (as opposed to narrative passages) ever shown.

Sincerely,

Bill

Tempt the Hand of Fate and it'll give you the "finger"!