Was gonna suggest the same thing, mall walking. Just leave your wallet and/or pocketbook at home!
You can bring a few bucks to buy a bottle of water or some other "lite" beverage to enjoy during or after your walk...
In the absence of malls, you might try contacting a local school district and asking if they have walking groups in the afternoons after school. Some places do that. I know our school system does. We have several buildings with a LOT of long hallway spaces.
You might also try signing up for a membership to use an indoor pool at a hotel (some places have programs for such things so the community may use the fitness center as well as hotel guests) or again, contacting a local school district that might have swimming facilities and an open swim night.
My wife and I used to take our son to a hotel pool for a while during the sumer. It was great for us both (she has CP and the water resistance is great therapy for her) but we got too busy to keep going unfortunately. I never really swam much in the pool, just moved around a lot, like a "power walk" with my head just above water so my body was pushing against as much water as possible for the resistance. It was great and I really felt like I was getting some decent exercise with it. Plus the place we went to had a nice little sauna in the locker room and a hot tub. And some fitness equipment which I never used, though I would have liked to try the stationary rower....
Open up the yellow pages in the phone book and call around some, get a little creative.
You amy want to think about mentioning your heart condition though, some people might say no to you in fear that you might drop dead in their hallway... An unreasonable concern no doubt, but then they tend to err on the side of caution, justified or not.
Oh yeah, we have a nice ice rink too here, though I haven't really skated on it in a few years. It's nice for a change of pace though.