Đakovo is a little town in the same Catholic diocese as Osijek, and its cathedral is a co-cathedral with Osijek’s cathedral. (Did you know that not every huge, grand, Gothic church in Europe is a cathedral? It’s only a cathedral if it’s the seat of the bishop.)
I’ve been to cathedrals in Finland, Austria, Hungary, Croatia, and the United States, and I’ve never seen a more beautiful cathedral than the one in tiny Đakovo. It’s not the grandest (though it certainly is grand) or the most ornamented. What it is is just pure, serene, elegant beauty.