Another vote for Barcelona! I loved, Loved, LOVED it...and I am in my forties, too. It was my favorite vacation of all time. It's a beautiful city...and fabulous for walking. My husband and I must've walked 15 or more miles a day. The city is like a mosaic, pieced together by many different and unique neighborhoods. We were there in late May, and the weather was absolutely gorgeous. Good food, Mediterranean Sea, La Rambla, and Gaudi architecture...it was just wonderful in every way. We EASILY filled an entire week, and still didn't get to see and do everything we wanted to. Have a great chick-trip, wherever you decide to go...sounds fun!

Stockholm - here is a link to our trip report from last May
http://tinyurl.com/jc22r

easy to walk, history, culture, great people, amazing food, surrounded by water, absolutely not one complaint.

here is link to my Copenhagen report, but if I had to return to one would personally return to Stockholm
http://tinyurl.com/j2v64

have fun wherever you choose !