When I feel like seeing new things I take a bike and go exploring small residential streets and neighborhoods. I've seen some very cool stuff just riding slow and looking. I've discovered guys working on hot rods in their garages, some great yard and landscaping ideas, some things I have no idea what they are, just weird and interesting stuff to look at. Unlike you, I've not explored the whole city, Denver's too big for that, but I don't have to go more than four or five miles from my house to find interesting things to see.
I've also met some great people on my bikes. I like to talk to folks and enjoy stopping and chatting with people. You don't always have to ride just for the sake of riding but use the bike as a means to an end. It's a good way to pass a couple of hours.
But that's just me