The Catoctin Aqueduct, or Aqueduct No. 3, ranks as one of the premiere stone structures on the C&O Canal. Aqueducts carried the canal's waters over creeks and rivers, allowing boats to float safely above the sometimes turbulent waters below. Engineers built the aqueduct for navigation, but they also created an elegant landmark. The iron scrollwork on the railing was a distinctive feature of the Catoctin Aqueduct.