It's a perfect opportunity for that elusive cheap date. Also, you can probably sneak in a bottle of wine or two… though one should be enough if they're really a cheap date.
Take a free tour of the Philadelphia Mint -- tours are self-guided and no reservations are needed, making this a good alternate option for a rainy day.
Located a short 20-minute drive from Center City -- traffic gods willing -- Valley Forge Park offers 3,600 acres of trails, history, and scenic views, making it a pretty sweet road trip. Not one of the nine best, but still pretty good.
Pop by while the park is open for business (May through September) -- there’s live music, oversized games, and hammocks!