The exterior is the whole point — one source flatly says don't bother with the inside unless you want the rooftop view. The park around it does most of the work: sakura over the moat in spring, strong autumn colors later (one vlogger argues autumn beats sakura here), and a river cruise that threads the moat if you've got the Osaka e-pass. In sakura season, walk in from Sakuranomiya station through the riverside trees instead of arriving by subway.