C&C per req:
1. Very nice. I like the simplicity and repeating pattern here. The only suggestion I would make is to perhaps crop the foreground closer to the start of the curve, basically, where you have the bright opening image right. I'm not sure that the dark foreground contributes anything.
2. ...
3, 4. I'm afraid these strike me as pretty much standard tourist shots. Try for a reshoot of #3 without all the people, and consider using both a polarizer and graduated ND filter to enhance colurs and reduce the dynamic range between sky and foreground.
Just my $00.02 worth - your mileage may vary.
~John