Creativity question: How do you destroy a city without killing the humans who live in it?

Four possibilities came up in our navy seminar that I can recall (to get the ball rolling):

1. A leaflet drop announcing that it will happen on a certain date to give time for humans to escape

2. Spreading a virus or noxious smell, like rotten egg gas, through the city which won't kill people but makes them highly motivated to be somewhere else (remember the 'hornet song'? 'He did not compel them to go 'gainst their will; he just made them willing to go!')

3. Providing a very appealing option for everyone to appear somewhere else (to receive food vouchers for life or something)

4. Ditto for negative reasons: if they're superstitious, encouraging them to relocate to avoid a Very Bad Thing Happening...