A massive structure or vehicle is destroyed spectacularly, but causes far less collateral damage than you'd expect.
Return of the Jedi: As discussed extensively here: http://www.theforce.net/swtc/holocaust.html
, the destruction of the 2nd Death Star should have caused a mass extinction on Endor.
Inependence Day: The destruction of the mothership would have a similar effect. In addition, each smaller 15 mile wide ship would release more energy than the most powerful nuclear bomb ever built when it was downed. The worst example is the ship that was destroyed when it was about to fire on Area 51. Instead of falling more or less straight down and burying Area 51 under millions of tons of rubble, it somehow manages to land in the desert beside it.
I'm sure there are other examples.