My wife's former car, a Civic and my Brother's CR-V have hidden filters. They are facing the firewall. On the CR-V you can reach through the opening in the right wheelwell and service it.
Not a Civic, but my old 90 Accord was like mentioned... it was horizontal facing the firewall on the back side of the engine. Definitely needed jackstands to get to it (was on the passenger side of mine).