One of the half-cities is permanent, the other is temporary, and when the period of its sojourn is over, they uproot it, dismantle it, and take it off, transplanting it to the vacant lots of another half-city.
Note
Sofronia is made of two half-cities. One is the fair: the roller coaster with its rigid humps, the carousel with its chains, the Ferris wheel of spinning cages, the big top with its clump of trapezes. The other is stone and cement: the bank, the factories, the palaces, the school, everything a serious city believes it must have. Every year the workmen come to take the second half apart, piece by piece, and carry it elsewhere.
You would expect the opposite: that the stone would stay and the wooden horses would leave. Calvino turns solidity on its head, and the scene takes him at his word: the fair never stops turning, while the half that looked eternal is lifted onto a trailer and driven off into the haze, leaving only a paler rectangle on the sand.
Tap the stone half and moving day begins, building by building; tap again and the trucks return, to rebuild the city as it was, or nearly. Tap the fair, and for a moment it spins faster. Here permanence is a trick of the light: it belongs to whatever never claimed to last.
Quotations are brief excerpts for the purpose of commentary. The full text is available in published editions. The Cities of Ottavia, Valdrada & the soundtrack are inspired by "Monument Valley" from ustwo games.