Dubrovnik is the most prominent tourist destinations in the Mediterranean Sea, a seaport and the centre of Dubrovnik-Neretva County. The names Dubrovnik and Ragusa co-existed for several centuries. Ragusa, recorded in various forms since at least the 10th century, remained the official name of the Republic of Ragusa until 1808, and of the city within the Kingdom of Dalmatia until 1918, while Dubrovnik, first recorded in the late 12th century, was in widespread use by the late 16th or early 17th century. According to Constantine Porphyrogenitus's De Administrando Imperio (c. 950), Ragusa was founded in the 7th century, named for a "rocky island" called Lausa, by refugees from Epidaurum (Ragusa Vecchia), a Greek city situated some 15 km to the south, when that city was destroyed in the Slavic incursions. The city boasts of many old buildings, such as the Arboretum Trsteno, the oldest arboretum in the world, dating back to before 1492. Also, the third oldest European pharmacy is located in the city, which dates back to 1317. A feature of Dubrovnik is its walls that run almost 2 kilometers around the city. The system of turrets and towers were intended to protect the vulnerable city. The walls of Dubrovnik have also been a popular filming location for the fictional city of King's Landing in the HBO television series, Game of Thrones.