The plains are interspersed with horst and graben structures, believed to have broken the Pliocene Pannonian Sea's surface as islands.

There are four types of biogeographical regions in Croatia: Mediterranean along the coast and in its immediate hinterland; Alpine in the elevated Lika and Gorski Kotar; Pannonian along the Drava and Danube; and Continental in the remaining areas.

[4] It lies mostly between latitudes 42° and 47° N and longitudes 13° and 20° E. Part of the extreme south of Croatia is separated from the rest of the mainland by a short coastline strip around Neum belonging to Bosnia–Herzegovina.

[12] Pursuant to the 1947 Treaty of Peace with Italy the islands of Cres, Lastovo and Palagruža and the cities of Zadar and Rijeka and most of Istria went to communist Yugoslavia and Croatia, while carving out the Free Territory of Trieste (FTT) as a city-state.

The former FTT's Yugoslav part was partitioned between Croatia and Slovenia, largely conforming to the area population's ethnic composition.

[14] In the late 19th century, Austria-Hungary established a geodetic network, for which the elevation benchmark was determined by the Adriatic Sea's average level at the Sartorio pier in Trieste.

[1] Italy and Yugoslavia defined their delineation of the continental shelf in the Adriatic Sea in 1968,[18] with an additional agreement on the boundary in the Gulf of Trieste signed in 1975 in accordance with the Treaty of Osimo.

Croatia also declared its Ecological and Fisheries Protection Zone (ZERP)—a part of its Exclusive Economic Zone—as extending to the continental shelf boundary.

[19] Croatia and Slovenia started negotiations to define maritime borders in the Gulf of Piran in 1992 but failed to agree, resulting in a dispute.

[20][21] Croatia's application to become an EU member state was initially suspended pending resolution of its border disputes with Slovenia.

[20] These were eventually settled with an agreement to accept the decision of an international arbitration commission set up via the UN, enabling Croatia to progress towards EU membership.

[22][23][24] The dispute has caused no major practical problems in areas other than the EU membership negotiations progress, even before the arbitration agreement.

Croatia took over the area with an agreement that allowed Montenegrin presence in Croatian waters in the bay, and the dispute has become far less contentious since the independence of Montenegro in 2006.

[31] The country is split into two main onshore provinces, a smaller part of the Pannonian Basin and the Karst Region in the Dinarides.

[32] The carbonate platform karst landscape of Croatia helped to create the weathering conditions to form bauxite, gypsum, clay, amphibolite, granite, spilite, gabbro, diabase and limestone.

[36] The largest islands in the Adriatic are Cres and Krk, each covering 405.78 square kilometres (156.67 sq mi); the tallest is Brač, reaching 780 metres (2,560 ft) above sea level.

Karstification there largely began after the final raising of the Dinarides in the Oligocene and Miocene epochs, when carbonate rock was exposed to atmospheric effects such as rain; this extended to 120 metres (390 ft) below the present sea level, exposed during the Last Glacial Maximum's sea level drop.

It is estimated that some karst formations are related to earlier drops of sea level, most notably the Messinian salinity crisis.

[49] The Pannonian Basin took shape through Miocenian thinning and subsidence of crust structures formed during the Late Paleozoic Variscan orogeny.

[50] Ultimately, up to 3,000 metres (9,800 ft) of sediment was deposited in the basin, and the sea eventually drained through the Iron Gate gorge.

[51] The results are large plains in the area bound by the rivers of Danube, Sava, Drava, and Kupa (including Slavonia, Baranya, and Syrmia).

[53] The two, as well as the Moslavačka gora mountains, are possibly remnants of a volcanic arc from the same tectonic plate collision that caused the Dinaric Alps.

Four of those are included in the Ramsar list of internationally important wetlands: Lonjsko Polje along the Sava and Lonja rivers near Sisak, Kopački Rit at the confluence of the Drava and Danube, the Neretva Delta and Crna Mlaka near Jastrebarsko.

Taking into consideration the overall water balance, the total Croatian water resources amount to 25,163 cubic metres (888,600 cu ft) per year per capita, including 5,877 cubic metres (207,500 cu ft) per year per capita from sources inside Croatia.

Higher wind velocities are more often recorded in cooler months along the coast, generally as cool northeasterly bora (sometimes exceeding 50 metres per second (160 ft/s) and southerly sirocco.

There are four types of biogeographical regions in Croatia: Mediterranean along the coast and in its immediate hinterland, Alpine in most of Lika and Gorski Kotar, Pannonian along the Drava and Danube, and continental in the remaining areas.

[65] Forests are also significant in the country, as they cover 26,487.6 square kilometres (10,226.9 sq mi) representing 46.8% of Croatia's land surface.

At the same time organic waste pollution levels decreased slightly, which is attributed to the completion of new sewage treatment plants; their number increased 20%, reaching a total of 101.

[5][81] The demographic history of Croatia is marked by significant migrations, including: the Croats' arrival in the area;[82] the growth of the Hungarian and German speaking population after the personal union of Croatia and Hungary;[83] joining of the Habsburg Empire;[84] migrations set off by the Ottoman conquests;[85][86][87] and the growth of the Italian-speaking population in Istria and Dalmatia during the Venetian rule there.

[114][115] The county borders have changed in some instances since (for reasons such as historical ties and requests by cities), with the latest revision taking place in 2006.