The bridge is one of the most valuable and iconic structures to appear in the history of humankind. Its primary function is to shorten the travel distance from one location to another by providing passage over bodies of water or terrain otherwise impassable. Bridges have always been an essential passageway to connect cities and countries.The earliest bridges were believed to have been made by nature in the form of fallen tree trunks or piles of rocks. Humans have used various materials to build bridges, with natives relying on local resources for construction materials, which may include rocks, tree trunks, bamboo, wood, and clay. As technology evolved, bridges have come to be made of both natural and human-made materials such as concrete, asphalt, steel, or even glass.According to the Guinness World Records, the Caravan Bridge in the Turkish city of Izmir, known in ancient times as Smyrna, is the oldest dated bridge in the world still in use. The Arkadiko Bridge in Greece is believed to be one of the oldest arch bridges still in use today. In India, you will find another kind of fascinating bridge made entirely from living tree branches, trunks, and roots in the state of Meghalaya. The two-story root bridge created in Cherrapunji is a prime attraction in Northeast India. The Living Root Bridges in Meghalaya are recognized as UNESCO World Heritage Sites.Some of the most expert bridge builders of ancient times were the Romans, who used diverse materials that evolved over time, including wood, brick, and various forms of stone. To cross rivers quickly, pontoon bridges were created using floats or boats that were laid side by side with wooden planks over the top. One defining feature of Roman bridges was the use of the arch. Two of the most famous Roman-engineered arch bridges still stand today: the Alcántara Bridge and the Pont du Gard, each serving different purposes.We now travel to Guangdong Province in China to visit the world’s first open-close bridge, which is still in use today. The Guangji Bridge was constructed in 1170 and crosses the Han River east of Chaozhou City.