Utilize the input text as a context reference, choose the right relationship between Merlin Properties and Madrid from the options. Options: 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.

** Spanish real estate firm Merlin Properties said it would expand its business to include hotels in Barcelona and Madrid through its purchase of property management company Testa .

Answer: headquarters_location