South Korea is a nation covered by apartments, so much so that from above, it resembles a coast-to-coast game of dominoes. Apartment buildings snake around mountains and form jarring clusters in the countryside. In cities, they align in grids that stretch for several kilometers.

Apartment houses first sprouted decades ago as a way to accommodate South Korea's booming middle class, and they were the picture of a nation in rapid ascent.

But the most remarkable thing about them isn't the national transformation they heralded, urban design experts say. It is their staying power.