Where’s the AT in Portuguese?

at the store

in the restaurant

on the subway

For some reason I just can't stop thinking about prepositions of place: in, on & at

Right in the middle of a hike. In the middle of my friend telling some crazy story about getting arrested on New Year's eve here (Rio de Janeiro).

I must have missed that day in 5th grade, but now I wanted to know all about prepositions. It all started when I realized that: in Portuguese you rarely get to say at. That's because it usually gets wrapped into a contraction.

The confusing thing is that the no and na can also mean in the or, on the as well.

The confusion comes from the fact that the word (actually, a preposition of place!) em cam mean in, on or at! And, as we know: em contracts with the articles o and a to make no and na.

Let's look at these three possibilities:

IN

ON

AT

So the next question is - when do we get to see at naked - on it's own, not in some contraction?

Can you think of any others?