Back with another doubt.
An incorrect sentence has been given as "Upon setting foot in the Gothic cathedral, the spectacularly stained glass windows amazed the camera wielding tourists."
Explanation given is-Upon is a preposition. The phrase upon setting foot in the Gothic cathedral contains the gerund setting. Who or what set foot in the cathedral? Logically, it must be the tourists, not the windows. However, the noun windows is the subject of the sentence, and so windows seems to be the subject of setting.
So, the correct sentence becomes-
Upon entering the Gothic cathedral, the camera-wielding tourists were amazed by the spectacular stained-glass windows.
But, I didn't understand the explanation clearly. So, thought this also can be the correct version-Upon setting foot in the Gothic cathedral, camera-wielding tourists were amazed by the spectacular stained-glass windows.
Please tell whether my version of correct sentence is right or wrong. Also, kindly help me in understanding the given explanation.