The Pontcysyllte Aqueduct and Canal in Wales is an impressive engineering structure built over 200 years ago that remains a tourist attraction today. It is the longest and highest cast-iron aqueduct in the world at 305 meters long and 38 meters high. In 2009, it became a UNESCO World Heritage Site, recognizing its historical significance alongside landmarks like the Great Barrier Reef. Crossing the aqueduct by boat provides a suspended feeling with a 38-meter drop to one side.