In Conquest of Planet Earth, the players are (usually green) bug-eyed space aliens doing the thing in the game title. There are ray guns, superheroes, strange events and, more to the point, temporal anomalies.
Here's the text of the Temporal Anomaly card:
Discard all Location cards on the board that do not currently have an Alien or marker on them, then shuffle all discard piles back into their respective decks.
The Capitol City lives in the middle of the board; it's put there at the beginning of the game. (All other locations are dealt from the Locations deck once someone moves a ship to an empty space.) It's pretty common for the Capitol City to have no Alien or conquest marker on it. (The capitol city is worth 5 victory points, in a game where victory happens at 8 points. It's also the best-defended location in the game.) However, the Capitol City is a truly singular card; it's a Location, but it quite definitely doesn't go in the Locations deck, because it's a double-sided card. (The other side is the Historical Monument, worth fewer victory points and less well-defended. If you play with that, it makes the game less of a race for the capitol.)
Since the Capitol City "can't" go in the Locations deck, what happens to it if it's unclaimed when Temporal Anomaly is drawn? Do you flip it to the other side? Randomly decide whether to flip it? Keep it intact? Shuffle it into the Locations deck anyway? Discard it, don't put it in the deck, and the Capitol City will never be seen again?