hard to pick one.

The old list (7 wonders) where written almost as a tour guide, the 7 most amazing human made things one can see. Obviously since then the tech has advanced and many have been destroyed by the hands of man or nature.

Even though it is hard to pick one (and the other 7 don't make sense) it is easy to cut some off (In my opinion)

grand canyon/ victoria falls : the 7 wonders are works of human ingenuity, these two are natural wonders. Don't fit in the list.

Saturn V: I know it is your choice, but the goal of a rocket is to fly in space, and so the truly wondrous part of it can't be appreciated


the next get harder:

Venice is unique and interesting, but is it truly a wonder?

Machu Picchu: might have been interesting in its day, but is nothing but ruins today.

The next three are even harder:

I have never seen the Taj Mahal. So it is hard to say if it is the most spectacular palace/building or not.

The Great wall and Panama canal is exceptional and well deserving of this title. (this is where I am leaning, go with something ancient or recent)