Complex sentence: Its footprint, as initially designed, would have blocked the proposed Congress Parkway extension; as a compromise, a hole for the Parkway was reserved in the base of the Post Office and utilized twenty years later.
Split into simpler sentences: Its footprint, as initially designed, would have blocked the proposed Congress Parkway extension. As a compromise, a hole for the Parkway was reserved in the base of the Post Office and utilized twenty years later.