Another one of my favorite pieces in the classical style is Carmina Burana. It has a neat history, with the texts having been found in a monastery and later put to music by Carl Orf. One of the most popular parts of the music is the “O Fortuna” piece, frequently used in movies that want a medieval sounding theme.
One of my favourite musical passages of all time is at 40:12 in this video, the “In taberna quando sumus”. It’s an incredibly odd piece of music, but just works somehow.