Which office is yours
What counts is your province of residence. Within it, fingerprints are taken at the Oficina de Extranjería or at Policía Nacional stations authorised to issue documents, which are not always the most central ones.
Some offices only take fingerprints, some only hand out cards, some do both. When you pick a procedure and province, the government site shows the offices that handle it: that list is the right one.
Choose all of them
Each office has its own calendar and releases slots on its own. Choosing them all multiplies your chances. In large provinces that may mean crossing the city; it almost always beats waiting weeks.
Before you go, check three things
That the address on your confirmation matches the office you are going to: in cities with several sites, you can’t switch on the day.
That the office handles your exact procedure.
What time they let you in: many won’t admit you more than fifteen minutes early.
Each province’s list
Every province page lists its offices, address, town and what each one handles, taken from the official government website.
General information, not legal advice. For questions about your own case, check the decision you were sent or ask a professional.