Behind my desk at work (not realy expensive but it is valuable to me) and when at the local swimming in the bike racks they have. Here I use two chains that go through the wheels frame and rack. Everything comes off the bike and the staff for the swim school and reception know both of my machines and keep an eye on them for me. It is also parked under the closed circuit video camera. I have had no one touch my bike in five years (touch wood it never happens) and only one person look at it (the staff from the pool just mentoned that before this gentlemen did anything remeber to smile for the camera and he simply walked away)
Either of my machines don't look that great and my weekly clean happens on Wednesday night so they look as un-loved as possible on Wednesday at swimming.