As sung by the elves in Rivendell. It's an iambic tetrameter hymn, and one of the longest texts in sindarin.
The hymn A Elbereth Gilthoniel is perhaps one of the most iconic texts in sindarin. It was published in the Lord of the Rings, and has since been subject of extensive debate and analysis. Tolkien fortunately provided a loose translation, and have in various publications (most recently PE17) explained the hymn in detail. It is certainly beautiful and very elvish.
O Elbereth Starkindler,
white-glittering, slanting down sparkling like a jewel,
the glory of the starry host!
Having gazed far away
from the tree-woven lands of Middle-earth,
to thee, Everwhite, I will sing,
on this side of the Sea, here on this side of the Ocean!