Complex sentence: On the top of the tower are four urns at the corners, and a cupola containing a bell, carried on Tuscan columns, and surmounted by a ball finial and a weather vane.
Split into simpler sentences: On the top of the tower are four urns at the corners, and a cupola containing a bell. The cupola is carried on Tuscan columns, and is surmounted by a ball finial and a weather vane.