A tunnel is a passageway that is dug underground or through a mountain, allowing people, vehicles, or trains to travel from one side to another. Tunnels can be found in many places, such as under rivers or through hills, and they help reduce travel time and avoid obstacles like traffic or natural barriers. One famous example of a tunnel is the Channel Tunnel, which connects England and France beneath the English Channel. This tunnel allows trains to travel quickly between the two countries, making it easier for people to visit and transport goods. Tunnels play a crucial role in modern transportation and infrastructure.