Any civilization capable of building such an enigmatic structure had to be far more technologically advanced than the Federation.

Apollo's keenest interest lay elsewhere, and he went down a lit-tle on the eastern slope, where the bulk of the vast enigmatic structure lay.

This enigmatic structure is one of many surviving examples of the Achaemenid architectural design.

The result is less the illusion that this picture was taken at night and much more a heightening of the essential mystery of such enigmatic structures.

It's an enigmatic structure, built by the Wolflings, not long before they were all wiped out.

All of those who'd passed through the enigmatic alien structure known as the Madness Maze had emerged changed, in body and mind.

Shortly before sunset we piled into the dinghy and puttered between corals until we reached the enigmatic structure.

As the enigmatic structure had moved out of the dawn belt into the morning, howling winds had risen.

They ran to the south edge of the island and stared at the massive, enigmatic structures in the southern bowl.

All of them contain enigmatic, ghost-like, structures.