Please read the following table in HTML format from a webpage and then answer the question in detail according to the table. Each table cell is defined by a <td> and a </td> tag. Each table row starts with a <tr> and ends with a </tr> tag. 'rowspan=m' and 'colspan=n' represents a cell spaning over 'm' rows and 'n' columns.

Webpage title:
List of World Heritage Sites of Poland
Table title:
World Heritage Sites
Table:
<table id='hittask' contenteditable='False'>
<tr> <th colspan=1 rowspan=1 > Name </th><th colspan=1 rowspan=1 > Image </th><th colspan=1 rowspan=1 > Location </th><th colspan=1 rowspan=1 > Date </th><th colspan=1 rowspan=1 > UNESCO data </th><th colspan=1 rowspan=1 > Description </th></tr>
<tr> <td class="highlighted"  colspan=1 rowspan=1 > Historic Centre of Kraków </td><td colspan=1 rowspan=1 > - </td><td colspan=1 rowspan=1 > Kraków 50°04′01″N 19°57′36″E / 50.067°N 19.96°E </td><td colspan=1 rowspan=1 > 11th–19th century </td><td colspan=1 rowspan=1 > 29; 1978; iv </td><td colspan=1 rowspan=1 > Kraków Old Town is the historic central district of Kraków, Poland. It is one of the most famous old districts in Poland today and was the center of Poland's political life from 1038 until King Sigismund III Vasa relocated his court to Warsaw in 1596. </td></tr>
<tr> <td colspan=1 rowspan=1 > Wieliczka and Bochnia Royal Salt Mines </td><td colspan=1 rowspan=1 > - </td><td colspan=1 rowspan=1 > Wieliczka 49°58′45″N 20°03′50″E / 49.979167°N 20.063889°E </td><td colspan=1 rowspan=1 > 13th-20th century </td><td colspan=1 rowspan=1 > 32; 1978; iv </td><td colspan=1 rowspan=1 > The Wieliczka Salt Mine, located in the town of Wieliczka in southern Poland, lies within the Kraków metropolitan area. The mine continuously produced table salt from the 13th century until 2007 as one of the world's oldest operating salt mines, for most of this time span being a part of the undertaking żupy krakowskie. </td></tr>
<tr> <td colspan=1 rowspan=1 > Auschwitz Birkenau, German Nazi Concentration and Extermination Camp (1940–1945) </td><td colspan=1 rowspan=1 > - </td><td colspan=1 rowspan=1 > Oświęcim 50°02′09″N 19°10′42″E / 50.035833°N 19.178333°E </td><td colspan=1 rowspan=1 > 1940-1945 </td><td colspan=1 rowspan=1 > 31; 1979; vi </td><td colspan=1 rowspan=1 > Auschwitz was a network of Nazi concentration and extermination camps built and operated by the Third Reich in Polish areas annexed by Nazi Germany during World War II. </td></tr>
<tr> <td colspan=1 rowspan=1 > Białowieza Forest </td><td colspan=1 rowspan=1 > - </td><td colspan=1 rowspan=1 > Belarus and Poland 52°40′00″N 23°50′00″E / 52.666667°N 23.833333°E </td><td colspan=1 rowspan=1 > N/A </td><td colspan=1 rowspan=1 > 33; 1979; vii </td><td colspan=1 rowspan=1 > The Białowieża Forest is an ancient woodland straddling the border between the two countries, located 70 km (43 mi) north of Brest (Belarus) and 62 km (39 mi) south-east of Białystok (Poland). </td></tr>
<tr> <td colspan=1 rowspan=1 > Historic Centre of Warsaw </td><td colspan=1 rowspan=1 > Warsaw Old Town Market Square 10.JPG </td><td colspan=1 rowspan=1 > Warsaw 52°14′59″N 21°00′44″E / 52.2498°N 21.0122°E </td><td colspan=1 rowspan=1 > 13th–20th century </td><td colspan=1 rowspan=1 > 30; 1980; ii, vi </td><td colspan=1 rowspan=1 > Warsaw's Old Town was established in the 13th century. Initially surrounded by an earthwork rampart, prior to 1339 it was fortified with brick city walls. </td></tr>
<tr> <td colspan=1 rowspan=1 > Old City of Zamość </td><td colspan=1 rowspan=1 > - </td><td colspan=1 rowspan=1 > Zamość 50°43′14″N 23°15′31″E / 50.720556°N 23.258611°E </td><td colspan=1 rowspan=1 > 1582–17th century </td><td colspan=1 rowspan=1 > 564; 1992; iv </td><td colspan=1 rowspan=1 > Jan Zamoyski commissioned the Italian architect Bernardo Morando to design the city that would be based on the anthropomorphic concept. The main distinguishing features of the Old Town have been well preserved since its establishment. </td></tr>
<tr> <td colspan=1 rowspan=1 > Castle of the Teutonic Order in Malbork </td><td colspan=1 rowspan=1 > - </td><td colspan=1 rowspan=1 > Malbork 54°02′23″N 19°01′40″E / 54.039722°N 19.027778°E </td><td colspan=1 rowspan=1 > 13th-14th century </td><td colspan=1 rowspan=1 > 847; 1997; ii, iii, iv </td><td colspan=1 rowspan=1 > The Castle in Malbork is the largest castle in the world by area. It was built in Prussia by the Teutonic Knights, a German Roman Catholic religious order of crusaders, in a form of an Ordensburg fortress. </td></tr>
<tr> <td colspan=1 rowspan=1 > Medieval Town of Toruń </td><td colspan=1 rowspan=1 > - </td><td colspan=1 rowspan=1 > Toruń 53°02′00″N 18°37′00″E / 53.033333°N 18.616667°E </td><td colspan=1 rowspan=1 > 12th–15th century </td><td colspan=1 rowspan=1 > 835; 1997; ii, iv </td><td colspan=1 rowspan=1 > Toruń has many monuments of architecture beginning from the Middle Ages, including 200 military structures. The city is famous for having preserved almost intact its medieval spatial layout and many Gothic buildings, all built from brick, including monumental churches, the Town Hall and many burgher houses. </td></tr>
<tr> <td colspan=1 rowspan=1 > Kalwaria Zebrzydowska: the Mannerist Architectural and Park Landscape Complex and Pilgrimage Park </td><td colspan=1 rowspan=1 > - </td><td colspan=1 rowspan=1 > Kalwaria Zebrzydowska 49°51′37″N 19°40′15″E / 49.860319°N 19.670719°E </td><td colspan=1 rowspan=1 > 1605-1632 </td><td colspan=1 rowspan=1 > 905; 1999; ii, iv </td><td colspan=1 rowspan=1 > The town is named after the religious complex (calvary) founded by Governor of Kraków Mikołaj Zebrzydowski on December 1, 1602. The complex is known as the Kalwaria Zebrzydowska park. </td></tr>
<tr> <td colspan=1 rowspan=1 > Churches of Peace in Jawor and Swidnica </td><td colspan=1 rowspan=1 > - </td><td colspan=1 rowspan=1 > Jawor, Świdnica 51°03′14″N 16°11′46″E / 51.054°N 16.196°E </td><td colspan=1 rowspan=1 > 1654-1657 </td><td colspan=1 rowspan=1 > 1054; 2001; iii, iv, vi </td><td colspan=1 rowspan=1 > The Churches of Peace in Jawor and Świdnica in Silesia were named after the Peace of Westphalia of 1648 which permitted the Lutherans in the Roman Catholic parts of Silesia to build three Evangelical churches from wood, loam and straw outside the city walls, without steeples and church bells. </td></tr>
<tr> <td colspan=1 rowspan=1 > Wooden Churches of Southern Lesser Poland </td><td colspan=1 rowspan=1 > - </td><td colspan=1 rowspan=1 > Lesser Poland Voivodeship 49°51′34″N 20°16′29″E / 49.859444°N 20.274722°E </td><td colspan=1 rowspan=1 > 15th-18th century </td><td colspan=1 rowspan=1 > 1053; 2003; iii, iv </td><td colspan=1 rowspan=1 > The wooden church style of the region originated in the late Medieval, the late sixteenth century, and began with Gothic ornament and polychrome detail, but because they were timber construction, the structure, general form, and feeling is entirely different from the gothic architecture or Polish Gothic (in stone or brick). </td></tr>
<tr> <td colspan=1 rowspan=1 > Muskauer Park / Park Mużakowski </td><td colspan=1 rowspan=1 > - </td><td colspan=1 rowspan=1 > Germany and Poland 51°33′01″N 14°43′36″E / 51.550278°N 14.726667°E </td><td colspan=1 rowspan=1 > 1815-1844 </td><td colspan=1 rowspan=1 > 1127; 2004; i, iv </td><td colspan=1 rowspan=1 > The Muskau Park is the largest and one of the most famous English gardens of Germany and Poland. Situated in the historic Upper Lusatia region, it covers 3.5 square kilometers (1.4 sq mi) of land in Poland and 2.1 km2 (0.81 sq mi) in Germany. </td></tr>
<tr> <td colspan=1 rowspan=1 > Centennial Hall </td><td colspan=1 rowspan=1 > - </td><td colspan=1 rowspan=1 > Wrocław 51°06′26″N 17°04′37″E / 51.107222°N 17.076944°E </td><td colspan=1 rowspan=1 > 1911-1913 </td><td colspan=1 rowspan=1 > 1165; 2006; i, ii, iv </td><td colspan=1 rowspan=1 > The Centennial Hall (formerly People's Hall) is a historic building in Wrocław. It was constructed according to the plans of architect Max Berg in 1911–1913, when the city was part of the German Empire. </td></tr>
<tr> <td colspan=1 rowspan=1 > Wooden Tserkvas of Carpathian Region in Poland and Ukraine </td><td colspan=1 rowspan=1 > Cerkiew bojkowska Smolnik.JPG </td><td colspan=1 rowspan=1 > (Brunary, Chotyniec, Kwiatoń, Owczary, Powroźnik, Radruż Smolnik, Turzańsk) Poland and Ukraine </td><td colspan=1 rowspan=1 > 16th - 19th century </td><td colspan=1 rowspan=1 > 1424; 2013; iii, iv </td><td colspan=1 rowspan=1 > Situated in the eastern fringe of Central Europe, the transnational property numbers a selection of 16 tserkvas, churches, built of horizontal wooden logs between the 16th and 19th centuries by communities of the Eastern Orthodox and Greek Catholic faiths. </td></tr>
<tr> <td class="highlighted"  colspan=1 rowspan=1 > Tarnowskie Góry Lead-Silver-Zinc Mine and its Underground Water Management System </td><td colspan=1 rowspan=1 > Dawna kopalnia srebra w Tarnowskich Górach.JPG </td><td colspan=1 rowspan=1 > Tarnowskie Góry 50°25′32″N 18°50′57″E / 50.4255°N 18.8493°E </td><td colspan=1 rowspan=1 > 16th century </td><td colspan=1 rowspan=1 > 1539; 2017; i, ii, iv </td><td colspan=1 rowspan=1 > Located in the Upper Silesian region of southern Poland, a major mining area of central Europe, the heritage site "includes the entire underground mine with adits, shafts, galleries and water management system. </td></tr>
</table>
Question:
How many UNESCO World Heritage Sites does Poland have?
Answer:
Poland has 15 UNESCO World Heritage Sites.