Istria is the largest peninsula in the Adriatic Sea. The peninsula is located at the head of the Adriatic between the Gulf of Trieste and the Bay of Kvarner. It is shared by three countries: Croatia, Slovenia, and Italy.
The geographical features of Istria include the Učka mountain ridge, which is the highest portion of the Ćićarija mountain range; the rivers Dragonja, Mirna, Pazinčica, and Raša; and the Lim bay and valley. Istria lies in three countries: Croatia, Slovenia and Italy. By far the largest portion (89%) lies in Croatia. “Croatian Istria” is divided into two counties, the larger being Istria County in western Croatia. Important towns in Istria County include Pula, Poreč, Rovinj, Pazin, Labin, Umag, Motovun, Buzet, and Buje. Smaller towns in Istria County include Višnjan, Roč, and Hum.
The northwestern part of Istria lies in Slovenia: it is known as Slovenian Istria, and includes the coastal municipalities of Piran, Izola and Koper, and the Karstic municipality of Hrpelje-Kozina. Northwards of Slovenian Istria, there is a tiny portion of the peninsula that lies in Italy. This smallest portion of Istria consists of the comunes of Muggia and San Dorligo della Valle, with the place of Santa Croce (Trieste) most to the north.
The ancient region of Histria extended over a much wider area, including the whole Kras plateau until the southern edges of the Vipava Valley, the southwestern portions of modern Inner Carniola with Postojna and Ilirska Bistrica, and the modern Italian Province of Trieste, but not the Liburnian coast which was already part of Illyricum.
Central Istria (Pazin) has a Continental climate.
North-Slovenian coast of Istria (Ankaran, Koper, Izola) has a Sub-Mediterranean climate.
West and south coast (Piran, Portorož, Novigrad, Rovinj, Pula) has a Mediterranean climate.
East coast (Rabac, Labin, Opatija) has a Sub-Mediterranean climate with Oceanic climate influences.
The warmest places are Pula, Rovinj, while the coldest is Pazin.
The Kvarner Gulf sometimes also Kvarner Bay, is a bay in the northern Adriatic Sea, located between the Istrian peninsula and the northern Croatian Littoral mainland. The bay is a part of Croatia’s internal waters.
The largest islands within the Kvarner are Cres, Krk, Pag, Rab and Lošinj. A portion of the Kvarner Bay, located between Cres, Krk, Rab and Pag is also called Kvarnerić (literally “little Kvarner”) or Italian: Golfo del Quarnerolo or Carnerolo, and the portion east of Krk and Rab is called Senj Channel.
The bay is notable for its depth, which allows for the city of Rijeka at its northernmost point to have a sea port that can accommodate Capesize ships.