Rivendell, or Imladris in its original Elvish tongue, is the realm of Elrond Half-Elven that was first described in The Hobbit and later expanded upon in The Lord of the Rings.
To convey the elegance of the elves, Alan Lee created Rivendell for the movies using art nouveau, which isn't often used in architecture. It's more associated with the artwork done by French painters at the turn of the 20th century, though its origins actually started a bit earlier.
Using art nouveau as architecture seems solely decorative and not used for practical uses, like defense. Then again, it could be both decorative and useful, like Gothic architecture.
So if Rivendell ever were to exist in real life, would art nouveau architecture be too decorative to use in a city, or would it be both ornate and practical? If the latter is possible, then how?