This thread is shit w/o @Mad_Son
Prepare to be underwhelmed. I have been a lot of beautiful places including most of those listed here already but...
One place I really liked was the Alpine Fault. This fault is a transform boundary between the Pacific plate and the Indo-Austrlian plate so you can easily stand on two continents at once.
This isn't anyone I know but this picture looks like the same/similar location as my favorite time climbing on the Alpine Fault.
I also don't know if this counts as visiting a geologic feature but when I used to work in oil it was a blast going offshore and checking out the cuttings circulating up the hole to see how mypredictions of 20k+ feet beneath the surface compared to reality.
To throw you a bone though, somewhere cool I went this past October was the Cliffs of Moher