Where to make out when your girlfriend hates PDA?

My girlfriend is really against public displays of affection, so when we go out anyone it's just holding hands and maybe a peck or two. But when we're alone she's fine. Now she stays in a res at uni, whereas I stay in a flat. I'm not allowed in the girls res. So the only time we're ever alone is at my flat. But I don't want it to feel like every time we come to my flat is makeout time. Can you please give me some suggestions (maybe you have a pda problem too?) as to where else we could go to be alone and make out so my flat doesn't get that stigma? Please don't say a hotel/motel :/