Complex sentence: The Three Sisters are three very similar self-anchored suspension bridges spanning the Allegheny River in downtown Pittsburgh, Pennsylvania at 6th, 7th, and 9th streets, generally running north/south.
Split into simpler sentences: The Three Sisters are three very similar self-anchored suspension bridges spanning the Allegheny River in Pittsburgh, Pennsylvania. They span the Allegheny at 6th, 7th, and 9th streets in downtown Pittsburgh, running generally north/south.