Enchantment or advancement.

[Bêthberry]

Originally Posted by OFS

For one thing, they are now old, and antiguity has an appeal in itself--distance and a great abyss of time. . . . They open a door on Another Time, and if we pass through, though only for a moment, we stand outside our own time, outside of Time itself, maybe.

So, perhaps it isn't magic per se, or even unreachable technology, but simply the distancing effect?