Well, how connected are you? Do you have a social network through work or your neighborhood or friends, and you could just send out a mass email that you're interested in forming an adventure group for city outings that meets, say, the first and third Thursdays of the month.
If you're not connected at all, have you tried Craig's List? Google Craig's list in your town, and there's a "community" section where people form groups. You could meet the first several times in open public areas so you don't end up with weirdos. I live in a beautiful exciting city too, and I googled our Craig's list just to check through the community postings before posting here, and sure enough, first hit up is a woman looking for a social network of women.
Best wishes. I'm in several women's groups, and they're great fun.