what does the adriatic sea border?
Kvarner Gulf Pag
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 The Adriatic Sea / ˌeɪdriˈætᵻk / is a body of water separating the Italian Peninsula from the Balkan peninsula and the Apennine Mountains from the Dinaric Alps and adjacent ranges . The Adriatic is the northernmost arm of the Mediterranean Sea , extending from the Strait of Otranto ( where it connects to the Ionian Sea ) to the northwest and the Po Valley . The countries with coasts on the Adriatic are Italy , Croatia , Albania , Montenegro , Bosnia @-@ Herzegovina , and Slovenia . The Adriatic contains over 1 @,@ 300 islands , mostly located along its eastern , Croatian , coast . It is divided into three basins , the northern being the shallowest and the southern being the deepest , with a maximum depth of 1 @,@ 233 metres ( 4 @,@ 045 ft ) . The Otranto Sill , an underwater ridge , is located at the border between the Adriatic and Ionian Seas . The prevailing currents flow counterclockwise from the Strait of Otranto , along the eastern coast and back to the strait along the western ( Italian ) coast . Tidal movements in the Adriatic are slight , although larger amplitudes are known to occur occasionally . The Adriatic 's salinity is lower than the Mediterranean 's because the Adriatic collects a third of the fresh water flowing into the Mediterranean , acting as a dilution basin . The surface water temperatures generally range from 30 ° C ( 86 ° F ) in summer to 12 ° C ( 54 ° F ) in winter , significantly moderating the Adriatic Basin 's climate . 

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 The Adriatic Sea is a semi @-@ enclosed sea , bordered in the southwest by the Apennine or Italian Peninsula , in the northwest by the Italian regions of Veneto and Friuli @-@ Venezia Giulia , and in the northeast by Slovenia , Croatia , Bosnia @-@ Herzegovina , Montenegro , and Albania — the Balkan peninsula . In the southeast , the Adriatic Sea connects to the Ionian Sea at the 72 @-@ kilometre ( 45 mi ) wide Strait of Otranto . The International Hydrographic Organization ( IHO ) defines the boundary between the Adriatic and the Ionian seas as a line running from the Butrinto River 's mouth ( latitude 39 ° 44'N ) in Albania to the Karagol Cape in Corfu , through this island to the Kephali Cape ( these two capes are in latitude 39 ° 45'N ) , and on to the Santa Maria di Leuca Cape ( latitude 39 ° 48'N ) . It extends 800 kilometres ( 500 mi ) from the northwest to the southeast and is 200 kilometres ( 120 mi ) wide . It covers 138 @,@ 600 square kilometres ( 53 @,@ 500 sq mi ) and has a volume of 35 @,@ 000 cubic kilometres ( 8 @,@ 400 cu mi ) . The Adriatic extends northwest from 40 ° to 45 ° 47 ' north , representing the Mediterranean 's northernmost portion . The sea is geographically divided into the Northern Adriatic , Central ( or Middle ) Adriatic , and Southern Adriatic . The Adriatic Sea drainage basin encompasses 235 @,@ 000 square kilometres ( 91 @,@ 000 sq mi ) , yielding a land – sea ratio of 1 @.@ 8 . The drainage basin 's mean elevation is 782 metres ( 2 @,@ 566 ft ) above sea level , with a mean slope of 12 @.@ 1 ° . Major rivers discharging into the Adriatic include the Po , Soča , Krka , Neretva , Drin , Bojana , and Vjosë . In the late 19th century , Austria @-@ Hungary established a geodetic network with an elevation benchmark using the average Adriatic Sea level at the Sartorio pier in Trieste , Italy . The benchmark was subsequently retained by Austria , adopted by Yugoslavia , and retained by the states that emerged after its dissolution . 

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 The Adriatic 's shores are populated by more than 3 @.@ 5 million people ; the largest cities are Bari , Venice , Trieste and Split . The earliest settlements on the Adriatic shores were Etruscan , Illyrian , and Greek . By the 2nd century BC , the shores were under Rome 's control . In the Middle Ages , the Adriatic shores and the sea itself were controlled , to a varying extent , by a series of states — most notably the Byzantine Empire , the Serbian Empire , the Republic of Venice , the Habsburg Monarchy and the Ottoman Empire . The Napoleonic Wars resulted in the First French Empire gaining coastal control and the British effort to counter the French in the area , ultimately securing most of the eastern Adriatic shore and the Po Valley for Austria . Following Italian unification , the Kingdom of Italy started an eastward expansion that lasted until the 20th century . Following World War I and the collapse of Austria @-@ Hungary and the Ottoman Empire , the eastern coast 's control passed to Yugoslavia and Albania . The former disintegrated during the 1990s , resulting in four new states on the Adriatic coast . Italy and Yugoslavia agreed on their maritime boundaries by 1975 and this boundary is recognised by Yugoslavia 's successor states , but the maritime boundaries between Slovenian , Croatian , Bosnian – Herzegovinian and Montenegrin waters are still disputed . Italy and Albania agreed on their maritime boundary in 1992 . 

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 During World War II , the Adriatic saw only limited naval action , starting with the Italian invasion of Albania and the joint Axis invasion of Yugoslavia . The latter led to the annexation of a large part of Dalmatia and nearly all the eastern Adriatic islands by Italy and the establishment of two puppet states , the Independent State of Croatia and the Kingdom of Montenegro , which controlled the remainder of the former Yugoslav Adriatic coast . In 1947 , after the Armistice between Italy and Allied armed forces and the war 's end , Italy ( now a republic ) and the Allies signed the Treaty of Peace with Italy . The treaty reversed all wartime annexations , guaranteed the independence of Albania , created the Free Territory of Trieste ( FTT ) as a city @-@ state , and gave communist Yugoslavia most of the Slovenian Littoral , as well as Istria , the islands of Cres , Lastovo and Palagruža , and the cities of Zadar and Rijeka . The FTT was partitioned in 1954 : Trieste itself and the area to the North of it were placed under Italian control , while the rest came under Yugoslav control . This arrangement was made permanent in the 1975 Treaty of Osimo . 

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 The countries bordering the Adriatic Sea are significant tourist destinations . The largest number of tourist overnight stays and the most numerous tourist accommodation facilities are recorded in Italy , especially in the Veneto region ( around Venice ) . Veneto is followed by the Emilia @-@ Romagna region and by the Adriatic Croatian counties . The Croatian tourist facilities are further augmented by 21 @,@ 000 nautical ports and moorings ; nautical tourists are attracted to various types of marine protected areas . 
