To pursue a point made in another thread, let's count how many times Marvel has actually destroyed a major city in one of their books. Now, destroyed is a subjective term, so let's give some latitude here. If it was major widespread distruction, we'll count it.
To start us off, I'll list a few:
Wasn't it part of New York City or was it Baltimore that The Red Skull had detonated in the first Man Out of Time arc by Brubaker?
Didn't the Submariner wipe out the waterfront of NYC in Fantastic Four Annual #1? Or was that merely a threat?
The Thing carried an atomic bomb on his back into the heart of Giaganto in FF #4 with the Submariner as villian.
"Central City" does not answer" from about FF #290 or so came just at the end of Byrne's run, but the city technically wasn't destroyed.
The Baxter Building was lifted off into space both in FF #6 by Doom and again in the mid 268-ish Byrne run by Kristoff as Doom. But that doesn't count as the whole city.
The Red Skull lifted Manhattan in a bubble back in Tales of Suspense #89-90 or so with Gil Kane drawing. Now, the city was returned in place without dropping it, but that's the most vivid image I can recall.
Oh, and who can forget Pittsburgh being whiped out by a blast in the New Universe? That's got to be tough to get over....
How about Kang dropping a bomb over New York(?) in the 12 part New Centurian Sword of Damacies arc over in Avengers volume 3 circa 40-52?
Anyone else got any examples to cite? :D