Opatija is situated in the Gulf of Kvarner in a sheltered position at the foot of Učka mountain, with Vojak peak at 1401 m. Opatija is located 90 km from Trieste by rail and 82 km from Pula by road. The city is geographically on the Istrian peninsula, though it is not in Istria county, but Primorje-Gorski Kotar county.
It is a popular summer and winter resort, with average temperatures of 10 °C in winter, and 25 °C in summer. Opatija is surrounded by beautiful woods of bay laurel. The whole sea-coast to the north and south of Opatija is rocky and picturesque, and contains several smaller winter resorts.
The old 14th-century Benedictine abbey, Opatija Sv. Jakova ("Abbey of Saint James"), from which the town derives its name (opatija means "abbey" in Croatian) is located in Park Svetog Jakova or Saint James's Park. Saint James's church, built in 1506 and enlarged in 1937, now stands on the same spot. The neo-Romanesque Church of the Annunciation with its pronounced green cupola, was designed in 1906 by architect Karl Seidl.
The city's most prestigious sight is the Villa Angiolina, which was built in 1844 by Iginio Scarpa, a rich merchant from Rijeka. This villa, transformed into a hotel, gave a boost to tourism to this town. It became a fashionable destination for the Austrian imperial family and Austrian nobility. Soon more luxury hotels and villas were built, such as the Hotel Kvarner, built in 1884, the Restaurant Kamelija and the Police station by the Keglević family. A new railway line was extended to Rijeka, from where it was possible to go by tram to Opatija. The Austrian emperor Franz Joseph I used to spend here several months during winter. Many of these late 19th-century luxury hotels and villas have survived to present times.
Opatija is known for the Maiden with the seagull, a statue by Zvonko Car (1956), which is positioned on a promontory by the Juraj Šporer art pavilion. It has turned into one of symbols of Opatija. A gilded variant of the statue Madonna, that once stood here but was demolished by communists after the end of WWII, now stands in front of Saint James's Church.
The town park Angiolina contains many species of plants from all over the world. It has been protected since 1968. Close-by, vis-a-vis Hotel Imperial, stands the statue The Fountain - Helios and Selena, a work of the Austrian sculptor Hans Rathautsky from 1889. There is a 12 km-long promenade along the entire riviera, the Lungomare from Volosko, via Opatija, to Lovran.
- Leo Sternbach (1908–2005), inventor of valium, born in Opatija
- Franz Graf von Meran (1839–1891), died in Opatija
- Theodor Billroth (1829–1894), died in Opatija
- Gyula Szapáry (1832-1905), died in Opatija
- Gustav Mahler (1860–1911), vacationed several times in Opatija (Abbazzia)
- Vladimir Nabokov
Legible signatures in the guest golden book
- Franz Joseph I of Austria
- Umberto II of Italy
- Carol I of Romania
- Oscar II of Sweden
- Grand Duke Boris Vladimirovich of Russia
- Adolphe, Grand Duke of Luxembourg
- Princess Stéphanie of Belgium
- Gyula Széchényi
and many others.