The Gibraltar territory currently contains an long section of the isthmus that links the Rock with mainland Spain. Spain does not acknowledge British sovereignty over Gibraltar beyond the fortified perimeter of the town as at 1704. The United Kingdom claims the southern part of the isthmus on the basis of continuous possession over a long period. As well as the airport, there are two substantial housing estates, a sports stadium, a secondary school, a marina, and a beach on this land, which de facto is an integral part of the territory of Gibraltar. Positions of each side One of the sources of the dispute is the lack of appropriate definitions of what had been actually ceded to Great Britain. The Treaty of Utrecht did not include any map or specific description of the ceded elements, so that Article X is subject to different interpretations from each side. According to Article X of the Treaty of Utrecht, dominion is ceded over the town and castle of Gibraltar, together with the port, fortifications, and forts thereunto belonging. Spanish position Spain does not acknowledge British sovereignty over Gibraltar, as they consider that the only part that was ceded was the fortified perimeter of the city, and the rest had no territorial jurisdiction (the literal phrase of the treaty is "the Catholic King wills, and takes it to be understood that the above-named propriety be yielded to Great Britain without any territorial jurisdiction"). Therefore, the Treaty would not have ceded any part of the isthmus. Spain considers that such an area was occupied by the UK since the 19th century (1815), and such "occupation of the isthmus [by the United Kingdom] is illegal and against the principles of the international law". For said reason, British sovereignty is not acknowledged by Spain, considering itself instead to be owner of the territory (see map). The British informed Spain of its intention to build barracks on the isthmus' neutral ground in 1815, which Spain agreed to for the duration of, and in order to assist in dealing with, a yellow fever epidemic in Gibraltar, and the buildings remained thereafter. The airport was built unilaterally by the British on another section of neutral ground in 1938, while Spain was fighting a civil war, thus further reducing the original size of the neutral ground. Referring to the current demarcation, Spanish official terminology always uses the word "fence" (verja in