Complex sentence: Broadway crosses the Harlem River on the Broadway Bridge to Marble Hill and then enters the Bronx, where it is the eastern border of Riverdale and the western border of Van Cortlandt Park.
Split into simpler sentences: Broadway crosses the Harlem River on the Broadway Bridge to Marble Hill. Afterward, it then enters the Bronx, where it is the eastern border of Riverdale and the western border of Van Cortlandt Park.