I'm have a girlfriend weekend planned for March. We're staying at the Marriott. Any ideas on what we can do?

If you are at all interested in Impressionist art, go out to the Barnes Foundation in Gladwynne (I think) It will be moving to a new location in Philly and it would be neat to see the collection in its original home before it moves. Contact them first, however. Visitor numbers are tightly controlled.
There is fun boutique shopping around Rittenhouse square.
I don't know where you are travelling from but a drive out to the Main Line to see some of the great old homes is fun.
A night in Chinatown would be a good group thing to do.

I suppose you mean the Marriot at the convention center. Nonetheless, Philly has a lot going on from the theatre and museums to great dining and clubs. Give me an idea of your age group and what you are interested in and I'll give you better info. Also, check out www.philly.com

We're high school friends-45 years old. Wow that's old. Is the Gallery shopping attached to the Marriott? I've been looking at different websites. It's pretty darn close right?

45 is not at all old!!! We are at our prime!! I haven't been in the Gallery in forever but from what I've seen on the outside you are better off spending your shopping time somewhere else. If you really want mall shopping, King of Prussia is one of the largest malls in the country and is 1/2 hour away. You may want to check to see when the Phila Flower Show is. It's one of the best in the country and usually around the beg. of March.

The National Constitution Center is a brand new museum (opened in the past year) dedicated to the US Constitution. It was wonderfully designed and is a very moving exhibit. I would highly recommend a visit during your stay. You can buy tix online for a particular day/time.

www.gophila.com is the best site for what's happening in Philly.

You can take a walk around Society Hill which is the historic residential area of the city, it's very nice and there are quite a few shops and restaurants in the surrounding neighborhoods. It's very walkable from all of the historic sites.

Avoid the Gallery! Otherwise, there are amazing museums, historical sites and restaurants to visit. Hopefully the weather will cooperate - Philly is a great city to just walk around and explore. Check out the Reading Terminal Market(next to the Marriott) for lunch. As to shopping, King of Prussia is amazing and you can drop a lot of $$$. Walnut street between Broad and Rittenhouse Square also has a number of lovely stores and boutiques. South Street is still totally funky. If you're on a budget, check out the Franklin Mills outlets up in NE PHL. Have fun!

If you want good shopping just ignore the Gallery and walk up Walnut Street. Between 14th (known as Broad Street) to 18th Street, there us great shopping. At 17th and Market there is a small mall in Liberty Center which is a nice complement to Walnut Street. At 18th and Walnut is Rittenhouse Park, grab a cup of coffee, sit on a bench in the park, and soak it all in. Try grabbing brunch at Sam's Morning Glory Diner (they have homemade ketchup and is a fancy diner with very good food, a big local hangout) near 10th and Bainbrdge - just take a cab. Enjoy! Philly is a GREAT city.