If you do not have information about the exact location of your relative who has traveled to Spain, here there are some steps that you can follow to try to locate it:
Communicate with other family and friends: ask other people nearby if they have any information about the whereabouts of your relative in Spain. They could have details about the place where or meet someone who can help.
Use social networks: verify if your relative has profiles on social networks such as Facebook, Twitter, Instagram, etc. Find your full name and current location or any other information that you can provide clues about your whereabouts. If you have access to an email account, verify whether they have received recent messages or if they have communicated with someone in Spain.
Get in touch with the embassy or consulate: if you are from a country different from Spain, you can communicate with the embassy or consulate of your country in Spain to inform them about your situation. They could provide guidance and assistance in the search for your family member.
Use websites and people search forums: there are different websites and forums that are dedicated to the search for missing or lost people. Try to search these resources and leave all the relevant information about your relative so that the community can help in the search.
Contract a private researcher: If you have tried all the previous resources without success, you could consider hiring a private researcher in Spain. They will have the necessary contacts and experience to locate your relative.
Remember that it is always important to keep calm and act organized in these cases. Do not hesitate to contact local or professional authorities to obtain additional help.