After thinking about it a bit more and wanting to vote, I went with Panama. Even though it is not the only canal in the world that can accommodate ocean vessels, it is the oldest and the most well known. It also helps bridge ancient with modern. The great wall is an incredible accomplishment. Bit there is one more (minor) fact of the 7 wonders. They were all the vision of a small time frame. The Pyramids are the ones that took the longest and they were each of one generation. The wall was built over many generations and even dynasties.