And its not really tunnels, its unique engineering. Other than there being stoplights and dams at the Jersey Harbor and the birthplace of the Jersey/Sweater, it really would be a nice place to visit, but, the attraction is the unique engineering approach that they took to keep water in their harbor during low tide. I know, many people would consider it boring.
The Falkirk wheel is an artsy lock system that was quite well engineered and planned. As far as water and energy efficiency, it takes the equivalent energy of using a computer for an hour to raise and lower a boat (thanks to Archimedes and displacement). The London Eye doesn't impress me as much, although, it is indeed a unique structure.
The Millau Viaduct's construction was quite interesting. Basically, the road sections were built on land and pushed over the pylons and put into place. Kansai International Airport is a man-made island with room for 3 large runways.
One of my favorite bridges is the Varina-Enon bridge. Nothing spectacular. Its on I-295 around Richmond, VA, but, its a cantilevered suspension bridge.
http://richmondcitywatch.com/infra_varina_enon.php
I'm a nerd.