Complex sentence: The palace's modern architecture (the dome has a diameter of 95 metres) makes it one of the most important indoor sports arenas in Europe, and after the works, it is able to accommodate up to 11,200 seated spectators.
Split into simpler sentences: The palace's modern architecture (the dome has a diameter of 95 metres) makes it one of the most important indoor sports arenas in Europe. After the remodeling, it is able to accommodate up to 11,200 seated spectators.