Commenters, you solved my double riddle, or more than half solved it.
The constellation with two sloping lines of stars is of course Gemini. It coyly peeped into view on the horizon of our picture. The famous moment a few minutes later, the prelude of winter evenings, when Castor is vertical above Pollux and Orion throws a leg up over the horizon, is shown in the splendid photograph that Eric David attached, with the addition of a bright planet to signal that the ecliptic runs through Gemini’s feet.
The other half of the answer is that the two geographical formations, mirroring Gemini as if they were a print of the constellation on Earth’s surface, are a long peninsula and the long inlet beside it: Baja California, and the Gulf of California, otherwise called Mar de Cortés.
A fanciful mirror to the constellation, not a perfect one. The peninsula and the gulf are narrower and closer together than the starry Twins. They were born together, though: it was the tectonic pushing up of the peninsula that enclosed the gulf, five million years ago. The gulf would be even longer, extending into U.S. California, but for silting by the Colorado River.
I saw the 1991 eclipse from the southern end of this double formation, but I didn’t expect anyone to pinpoint that. The mighty eclipse’s track slanted across the southern ends of both the peninsula and the gulf, and people went to both sides to see it. You guessed “Baja ha ha!” and “Cabo de San Lucás,” probably because you had been there, but I was one of those on the other side, the mainland, where this nearly central eclipse passed nearly overhead. The coastal village we went to was Sayulita. The one we’re now going to, just along the same coast, is called Rincón de Guayabitos, which I think means “nook of the little guava trees” – I’ll tell you what it’s like after we experience it.
The meteors we should see from there, in the night between December 13 and 14, are the Geminids, as you also couldn’t fail to guess. The peak of the shower is expected around 6 Universal Time, which is midnight by U.S. Central time. The Moon will be New on December 18. So the circumstances could hardly be better.
Here is what it should look like for us as the Geminid radiant rises into view.
Latitude 21 is inside the Tropic of Cancer, where the noon Sun is overhead at the June solstice; and it is close to where the eclipsed Sun was overhead in July 1991 and the Geminid radiant will be overhead at midnight.