55874
Originally built on former marshland of the submerged Poltva River , the Lviv Opera now sits at the end of Freedom Avenue ( ) , the tree-lined centerpiece of Lviv 's historic Old City , a UNESCO World Heritage Site located in the city 's Halych district .
 Poltva River, Lviv Opera, Freedom Avenue, Lviv, Old City, UNESCO World Heritage Site, Halych
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Poltva River, Lviv Opera, Freedom Avenue, Lviv, Old City, UNESCO World Heritage Site, Halych