In more than one place.
For example...The Final Dungeon. And the Ice Glacier area. And the Battle Arena in the Golden Saucer. And I think there was one, just one...in the temple of the ancients that you could fight in the Nipponese version.

Here is a question if I am right, that is.

How old is Cloud, Tifa, Barret, Cid, and...Yuffie?