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.

Surrounded by a team of Syriza higher-ups, Lafazanis has stepped up public appearances in Athens and elsewhere in the country that "strongly resemble the start of a campaign", a Syriza member said on condition of anonymity.

Answer: headquarters_location