Festivus

Each city in Spain has their own bank holidays. (Some bank holidays are common to most of Spain, but rules are more complex than you would expect.)

See https://festivus-es.github.io/festivus/ for iCal URLs for some cities.

You can submit new cities as pull requests.

Alternatively, https://www.seg-social.es/wps/portal/wss/internet/CalendarioLaboral/ seems to be the most complete official source, besides city hall websites.