my dad has been to pretty much every Red Star vs Partizan games in the 70's and 80's, he's got some stories
also most of the games between Partizan vs Dinamo and Hajduk.
most of the games between Red Star and Partizan had about 105,000 in the stands, but i think the stadiums have been scaled down since. they're also really close to each other. right around the corner.