Learn Finnish: Me olemme torilla. - We are at the market square.

Torilla uses the adessive case ending -lla, which usually translates to "on" or "at". In Finnish, open spaces like a market square (tori), a street, or a yard are considered "outside" or "on top of" spaces, so they take this external location ending rather than the internal "in" ending.

Why does it use the -lla ending instead of -llä?

This is because of vowel harmony. The word tori has the back vowel o. Because it contains a back vowel, the ending must also use the back vowel a (-lla), rather than the front vowel ä (-llä).

Could I drop the word me and just say Olemme torilla?

Yes! In Finnish, the verb ending -mme already tells us that the subject is "we". Because of this, it is very common to drop the pronoun me and simply say Olemme torilla.

How would the ending change if we were inside an indoor market?