Complex sentence: One of the first and most prominent modernist structures was Ludwig Mies van der Rohe's Toronto-Dominion Centre was one of the most prominent of the early glass panelled office towers, which would be imitated around the world.
Split into simpler sentences: One of the first and most prominent modernist structures was Ludwig Mies van der Rohe's Toronto-Dominion Centre. The T-D Centre was one of the most prominent of the early glass panelled office towers, which would be imitated around the world.