Answer the following question: Information:  - Sofia (or or ;) ("Sofiya",) is the capital and largest city of Bulgaria. The city has a population of 1.26 million, while 1.68 million people live in its metropolitan area. The city is located at the foot of Vitosha Mountain in the western part of the country, within less than drive from the Serbian border. Its location in the centre of the Balkan peninsula means that it is the midway between the Black Sea and the Adriatic Sea, whereas the Aegean Sea is the closest to it.  - The Adriatic Sea 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 Albania, Bosnia and Herzegovina, Croatia, Greece, Italy, Montenegro 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 . 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 in summer to in winter, significantly moderating the Adriatic Basin's climate.  - Vitosha, the ancient "Scomius" or "Scombrus", is a mountain massif, on the outskirts of Sofia, the capital of Bulgaria. Vitosha is one of the symbols of Sofia and the closest site for hiking, alpinism and skiing. Convenient bus lines and rope ways render the mountain easily accessible. Vitosha has the outlines of an enormous dome. The territory of the mountain includes Vitosha nature park that encompasses the best known and most frequently visited parts. The foothills of Vitosha shelter resort quarters of Sofia; Knyazhevo quarter has mineral springs. Vitosha is the oldest nature park in the Balkans. The mountain emerged as a result of volcanic activity and has been subsequently shaped by the slow folding of the granite rock layers and a series of gradual uplifts of the area. It appears dome shaped at first sight, but the mountain, 19 km long by 17 km wide, actually consists of concentric denudational plateaus rising in tiers one above the other. Vitosha is separated into four main parts whose main ridges gather at a crown known as "Cherni Vrah" (""Black Peak""). This is the highest point of the mountain at 2290 m and is one of 10 peaks of Vitosha over 2000 m in height.  - Turkey, officially the Republic of Turkey (Turkish: ), is a transcontinental country in Eurasia, mainly in Anatolia in Western Asia, with a smaller portion on the Balkan peninsula in Southeast Europe. Turkey is a democratic, secular, unitary, parliamentary republic with a diverse cultural heritage. Turkey is bordered by eight countries: Greece to the west; Bulgaria to the northwest; Georgia to the northeast; Armenia, the Azerbaijani exclave of Nakhchivan and Iran to the east; and Iraq and Syria to the south. The Aegean Sea is to the west, the Black Sea to the north, and the Mediterranean Sea to the south. The Bosphorus, the Sea of Marmara, and the Dardanelles, which together form the Turkish Straits, divide Thrace and Anatolia; they also separate Europe and Asia. Turkey's location has given it geopolitical and strategic importance throughout history.  - A city is a large and permanent human settlement. Although there is no agreement on how a city is distinguished from a town in general English language meanings, many cities have a particular administrative, legal, or historical status based on local law.  - The Aegean Sea  is an elongated embayment of the Mediterranean Sea located between the Greek and Anatolian peninsulas, i.e., between the mainlands of Greece and Turkey. In the north, it is connected to the Marmara Sea and Black Sea by the Dardanelles and Bosphorus. The Aegean Islands are within the sea and some bound it on its southern periphery, including Crete and Rhodes.  - Lyulin ( Bulgarian :  or   ) is a range of hills in western Bulgaria , located several kilometres west of Sofia . The highest point is Dupevitsa Peak ( 1,256 m ) . The Buchino Pass divides the hills into two , a western and an eastern part . Bonsovi Polyani are a popular tourist attraction . On the slopes of Liulin are some of the most beautiful quarters of Sofia - Knyazhevo , Gorna Banya and Bankya , known with their mineral springs .  - Serbia, officially the Republic of Serbia, is a sovereign state situated at the crossroads of Central and Southeast Europe, covering the southern part of the Pannonian Plain and the central Balkans. Relative to its small territory, it is a diverse country distinguished by a "transitional" character, situated along cultural, geographic, climatic and other boundaries. Serbia is landlocked and borders Hungary to the north; Romania and Bulgaria to the east; Macedonia to the south; and Croatia, Bosnia-Herzegovina, and Montenegro to the southwest; it also claims a border with Albania through the disputed territory of Kosovo. Serbia numbers around 7 million residents, and its capital, Belgrade, ranks among the largest cities in Southeast Europe.  - The Black Sea is a body of water between Eastern Europe and Western Asia, bounded by Bulgaria, Georgia, Romania, Russia, Turkey, and Ukraine. It is supplied by a number of major rivers, such as the Danube, Dnieper, Rioni, Southern Bug, and Dniester. The Black Sea has an area of (not including the Sea of Azov), a maximum depth of , and a volume of . It is constrained by the Pontic Mountains to the south and by the Caucasus Mountains to the east, and features a wide shelf to the northwest. The longest east-west extent is about .  - Romania is a sovereign state located in Southeastern Europe. It borders the Black Sea, Bulgaria, Ukraine, Hungary, Serbia, and Moldova. It has an area of and a temperate-continental climate. With 19.94 million inhabitants, the country is the seventh-most-populous member state of the European Union. The capital and largest city, Bucharest, with its 1,883,425 inhabitants is the sixth-largest city in the EU.  - Greece (' ), officially the Hellenic Republic (Greek: ' ), historically also known as Hellas ("" ), is a country in southeastern Europe.  Greece's population is approximately 10.955 million as of 2015. Athens is the nation's capital and largest city, followed by Thessaloniki.  - Bulgaria (tr. '), officially the Republic of Bulgaria (tr. '), is a country in southeastern Europe. It is bordered by Romania to the north, Serbia and Macedonia to the west, Greece and Turkey to the south, and the Black Sea to the east. With a territory of , Bulgaria is Europe's 16th-largest country.    What entity does 'lyulin mountain' has the relation 'instance of' with?
Answer:
mountain