Complex sentence: It lies south of the Miami River, extending south to SE 26th Road (the Rickenbacker Causeway), and is split into two subdivisions by Broadway, into Upper Brickell and Lower Brickell.
Split into simpler sentences: It lies south of the Miami River, extending south to SE 26th Road (the Rickenbacker Causeway). Brickell is split into two subdivisions by Broadway, Upper Brickell and Lower Brickell.