Complex sentence: The bridge was built on 20 pillars of stone blocks, is 1135 m long, 14.55 m wide and 18.60 m high, the heads having each a portal monument, whose relics are seen on both sides of the Danube.
Split into simpler sentences: The bridge was built on 20 pillars of stone blocks, was 1135 m long, 14.55 m wide and 18.60 m high. Each head had its own portal monument, whose remains can still be seen on both sides of the Danube.