Where to Hide a Second Set of Keys

Lifehacker has this suggestion:

If you want a hide-a-key option for your house, and you want something that will blend in well with your yard, weblog Factory Direct Craft has a simple solution. All you need is an old prescription pill bottle.

Take your prescription pill bottle and remove all the labeling. Then decide on what you want to disguise your bottle with. The blog suggests a pine cone, but obviously, if you don't have pine cones around your house, you'll want to use something else (like a rock). Then attach it to the bottom of the pill bottle with some sort of epoxy adhesive. You don't want to use hot glue or anything else that won't withstand the elements. 

Once your spare key is inside, make sure you hide it somewhere that isn't near your door (where it'd be easy to stumble upon). Once you've picked your spot, dig a small hole and bury it with the pine cone or rock on top. You're all set!

Because I live in the city, this wouldn't work for me. What I do, and have done in other cities, is buy two or three magnetic key holders, put duplicatekeys in them and place them at various spots within a block or so of my apartment.

I put them just far enough away from my residence so that if anyone discovers the keys, they wouldn't associate them with my place, but close enough so that they wouldn't be a hassle to get to.

I currently have one on the back side of a parking sign, the back side faces a concrete wall, so it is very unlikely anyone would ever spot it.

I have another set in the stairwell of a hotel that is near me, behind a metal pipe. 

And I have placed another set on a metal fence that is covered with ivy.

It's possible, though very unlikely, that someone might come along and spot one of my hiding places, but very unlikely that all three would be spotted.

Only once did I ever lock myself out of an apartment, but when I needed the keys, three years after I hid them, they were right where I placed them.