prepositions - Should I use in, on or at for locations like this: "I am {on/at/in} the railway station"?

Which prepositions are correct?

I am {on/at/in} the railway station.
I am {on/at/in} square.

Answer

I am on the railway station.

means you are on top of the railway station (like on the ceiling). Not likely.

I am at the railway station.

means you are there, location wise.

I am in the railway station.

means you are inside (the perimeter) of the railway station.