Where is the external air temperature sensor located on a 1999 Mercedes C-Class?

Its been bothering me that I couldn't remember for the whole day. On the probably similar 1998, and other MBs I've had, its behind the front license plate.

This should not be confused with the Oxygen sensor that is part of the ignition/pollution system and is reported faulty by a computer code. That's under the hood and part of the air intake system.