It's Fun to Know: About Tunnels
The world's longest underwater tunnel (at 31 miles) is the Chunnel, which links France and England beneath the English Channel. It's been open for 15 years.
The world's soon-to-be longest tunnel (at 34.5 miles) is in the Swiss Alps. It will be ready for trains in 2017.
Meanwhile, New York City is in the process of replacing its crumbling aqueduct infrastructure (made up of tunnels that carry water). The new system will be 60 miles of tunnels between 10 and 24 feet wide. Started in the 1970s, the project is expected to be completed by 2020.
(Source: Discover Magazine)