Gulliver in Laputa

Gulliver's third voyage out has him shipwrecked again.  This time he washes up on an uninhabited island.  He is alone, but not for long.  Soon another island glides down from the sky.  He catches their attention and is brought aboard.  He learns that the flying island is named Laputa.
Gulliver soon finds that "the people of their island had their ears adapted to hear"the music of the spheres, which always played at certain periods...".  They live a mental life, with their heads both literally and figuratively in the clouds.  In fact, they get so lost in thought that they employ a system of servants to flap their mouths and ears when it is time to speak or listen. 
Laputa is the capitol of a group of islands.  Swift has an interesting explanation for how the island floats, an embedded giant magnet like rock.  Whoever rules the island, rules their neighbors, since the airborne position is an enormous threat.  Interestingly, the women of Laputa are desperate to get down to the ground.
Gulliver gets down to solid ground as he is allowed to visit the island Balinbarbi.  This is a land that has prosperity and strange mixes of desolation.  He soon finds out that forty years prior, a group of men went up to Laputa.  After five months they returned with ideas on improving everything.  Unfortunately:

The only inconvenience is, that none of these projects are yet brought to perfection; and in the mean time, the whole country lies miserably waste, the houses in ruins, and the people without food or clothes. By all which, instead of being discouraged, they are fifty times more violently bent upon prosecuting their schemes, driven equally on by hope and despair; . . . 

Some resisted:

that some few other persons of quality and gentry had done the same [stuck with the old ways], but were looked on with an eye of contempt and ill-will, as enemies to art, ignorant and ill common-wealth's men, preferring their own ease and sloth before the general improvement of their country."

What a perfect description of the people who think they can simply theorize better ways without practical experience.  Also a great description of the way they think of those who are skeptical.  Gulliver then travels to the academy where he finds out all of the wonderful research that is going.  I highly recommend this section (book three, chapters five and six) as it is simply hilarious. 
After some time, Gulliver goes to another island, Luggnagg.  The interesting thing there is the occasional birth of an immortal, named a Struldbrug.  Gulliver thinks this would be a wonder, but instead it's a curse.  The Stuldbrugs grow old and senile and frankly the whole deal sounds awful.
Eventually Gulliver gets to Japan where he can catch passage on a Dutch ship.  He has to do some fancy footwork to avoid 'stamping on a cross', a custom the Japanese have enforced on the Dutch to try and keep Christians out.  He succeeds and finally gets back home.