A micrometeorite found in Antarctica was shed from rock formations like this one. They look too regular to be natural. Is this tiny space rock part of an ancient alien castle?

Nope - it's just a tiny chunk of basalt.

Yesterday an international group of researchers announced their discovery in the Proceedings of the National Academy of Sciences, explaining that the meteorite was made from a form of basalt that had never before been encountered in Earth - or in a meteorite. The image you see above was captured on Earth: It's part of a basalt formation on the Scottish island of Staffa, photographed by Jim Richardson for National Geographic. Here is another example of the self-assembling architecture of basalt formations, from Turkey:

The tiny meteorite discovered in Antarctica is only 100–200 micrometers in diameter - so small that it doesn't suffer the same kinds of damage that a larger meteorite might as it hits the atmosphere. So the micrometeorite gives scientists a more accurate picture of the crusts of local planets and asteroids that likely spawned the space-going rock. The researchers report:

This micrometeorite is unlike any other basalt known in the solar system as revealed by isotopic data, mineral chemistry, and trace element abundances. The discovery of a new basaltic asteroidal surface expands the solar system inventory of planetary crusts . . .

It's likely that this basalt came from formations on other planets that look like these otherworldly formations on Earth. Basalt on Earth is often released in liquified form during volcanic eruptions. If it hardens rapidly enough, it forms into regular shapes that look like human-made columns and tiles. Here you can see that effect in Ireland:

Basalt is already associated with extraterrestrials - at least, in pop culture. The aliens in Close Encounters of the Third Kind arrive in ships that hover over Devil's Tower in Wyoming, a huge basalt formation.