What is the relationship between Syriza and Athens in the context of the input sentence. Choose an answer from: product/material produced; manufacturer; distributed by; industry; position held; original broadcaster; owned by; founded by; distribution format; headquarters location; stock exchange; currency; parent organization; chief executive officer; director/manager; owner of; operator; member of; employer; chairperson; platform; subsidiary; legal form; publisher; developer; brand; business division; location of formation; creator.

Even Germany's Wolfgang Schaeuble, who last month floated a Greek exit from the euro as Tsipras hesitated to agree terms with fellow leaders, sounded upbeat, if still wary of a new tone in Athens that caused an angry split in Tsipras' leftist party, with nearly a third of Syriza lawmakers rebelling in parliament.

Answer: headquarters_location