Analyze the relationship between 'Syriza' and 'Athens' within the context of the input sentence.
Options: chairperson, brand, platform, headquarters location

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.
headquarters location