Lyric discussion by smartalek 

Don't know enough about the Biblical David/Bathsheba story to contribute anything useful (except that it's supposed to also be at least part of the inspiration for the great Leonard Cohen song, "Hallelujah," which is now best-known for being the "Shrek" song, in its cover by John Cale). But it's pretty clear that in the verse about "the vanity of an ancient king," Sting is referring directly to the famous poem by the early-19th-century English Romantic poet Shelley, called "Ozymandias." (Don't forget Sting was a schoolteacher for two years before breaking out as a rock-star. Pretty much every English schoolkid would know this work.)
The point of the poem (the greatest works of the most powerful man, a king, are nothing in the face of eternity) plays into the point of the song (the singer's kingdom and works mean nothing without his lover's love). Here's the whole poem:

Ozymandias

  by Percy Bysshe Shelley

I met a traveler from an antique land Who said: Two vast and trunkless legs of stone Stand in the desert. Near them, on the sand, Half sunk, a shattered visage lies, whose frown, And wrinkled lip, and sneer of cold command, Tell that its sculptor well those passions read Which yet survive, stamped on these lifeless things, The hand that mocked them, and the heart that fed; And on the pedestal these words appear: “My name is Ozymandias, king of kings: Look upon my works, ye Mighty, and despair!” Nothing beside remains. Round the decay Of that colossal wreck, boundless and bare The lone and level sands stretch far away.

If you want to know more about the poem, its author, meaning, background:

en.wikipedia.org/wiki/Ozymandias

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