The Hotel Kvarner is the oldest hotel on the Adriatic coast, opened in 1884 and still operating today in its original white neoclassical building overlooking the sea. As architecture it is more restrained than some of Opatija's grander later constructions, but its historical significance is considerable — it was the building that announced Opatija as a public resort rather than a private aristocratic retreat, and it drew the first wave of the wealthy central European clientele that would define the town's character.
The building has been renovated and updated over the decades, but the facade and some of the public spaces retain their original character. Non-guests are welcome to have coffee or a drink on the terrace, which has one of the better views of the Kvarner Gulf in the town centre. Worth a look if you are interested in Opatija's Habsburg-era history.