Starting to get into classical music, looking for some hidden gems that I shouldnt miss?

Some classical music I like

Beethoven, Chopin (maestoso palonaise No.6), Mussorgsky's A night on Bald Mountain, Schubert (ave maria)

I know im probably missing a life time of great music out there so any suggestions would be great thanks!
Update: Hey I really like Dance Of The Knights thanks
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