I want to take a trip and I will be traveling alone. Which of these options would offer the most to do?

I enjoy restaurants/bars, culture, zoos/aquariums, shopping, outdoor adventures or just hiking/biking through a park, some history and I love sight-seeing %26amp; visiting city icons like the St. Louis Arch, the Space Needle or a famous port or pier. I am in my early 30's. Here are the options:

Baltimore

Chicago

Denver

Hartford, CT

Minneapolis/St. Paul

Portland

Providence

Reno/Tahoe

Salt Lake City

Seattle/Tacoma

Spokane

I would also like to hear suggestions about what to do in these places. I would like a city with good infrastructure, where it is fairly easy to get along, and I would like a city with a friendly culture, should I need directions or help getting around. Nice weather would be good (traveling near the end of September), but I don't mind some rain here and there.I want to take a trip and I will be traveling alone. Which of these options would offer the most to do?
What, no Boston?



Added: Well, since Boston is out... Chicago has tons to do. Amazing architecture. Blues clubs, good transit, fine museums. Take the architectural boat ride. Very friendly. Go up the Hancock or the Sears Tower. Sept is perfect -- winter is brutal, summer is sweltering.



Denver is good for a short trip. Friendly people, day trips to the mountains, good downtown. Very dry if you are from the lowlands, take eyedrops and chapstick.



Providence is good for a day or two, then go to Newport for the mansions and some of the beaches down state for hiking/nature. Great restaurants in Providence, the Design Museum is cool. Otherwise not much.



Reno is also good for a base. If you don't gamble, the casino hotels are a great bargain. Virginia City and Carson City are a good day trip. Tahoe is wonderful for hiking, boating, etc. Great scenery.



Seattle is good on its own. Wonderful food, great bookstores. Side trip down to Tacoma to see the glass museum.



I'd skip Hartford, not much there. Haven't been to the others for longer than it takes for the train to stop or to transfer planes.I want to take a trip and I will be traveling alone. Which of these options would offer the most to do?
One word....Philadelphia