The caves of Alpha Onias III
Alpha Onias III was a Class M planet located in the Alpha Onias system near the Romulan Neutral Zone. Barash, a humanoid child, was hidden in a cavern by his mother after their homeworld was attacked in the mid-24th century. The cavern was equipped with neural scanners that were able to transform matter into any form imagined, so that Barash could live in safety. (TNG: "Future Imperfect")