Keep in mind you’ll be visiting a reproduction of the caves, not the actual one. Note the free days.
From the website about advance tickets:
“Advance
In advance through Banco Santander's online sales platform .
Information regarding advance purchase:
Tickets purchased online are only valid for the service, date, and time indicated. Failure to comply with the indicated time will result in the holder being subject to the same access and waiting conditions that apply to visitors without tickets.
To purchase free tickets, you must present the corresponding official document, valid and clearly updated, at the box office. If, after verification of the aforementioned accreditation, the requirements are not met, you will be required to pay the standard rate and an entry time will be assigned based on available capacity.
The purchase of general admission tickets does not require validation at the box office. Any visitor with a general admission ticket may present themselves directly at the museum entrance doors.
Tickets must be purchased in advance at least one day before the visit, never on the same day.
Tickets purchased through advance sales services cannot be exchanged or refunded.
Punctuality is essential (15 minutes before the selected time). Otherwise, you will lose your right to entry.
Tickets for Saturday afternoons and Sundays are always free and can only be obtained at the museum ticket office on the day of the visit.”
Free admission (for all visitors)
Saturdays from 2:00 p.m. and Sundays all day
April 18, International Day of Monuments and Sites
May 18, International Museum Day
October 12, Spanish National Holiday
December 6, Constitution Day
Free admission (accreditation required)
Persons under 18 and over 65.
Students between 18 and 25.
If you’re spending the night in Santillana Del Mar, consider staying at the Parador Gil Blas. Also, if there for a night you’ll get to experience the town without all the day trippers. Finally, while walking around the town, especially near Collegiate Church of Santillana you may notice round brass plaques with the Camino de Santiago symbol inlayed/embedded among the cobbles. They signify you’re on a part of the Camino.
In 2017 we had a good meal at Restaurante Casa Miguel. We ordered the fixed price menu of the day and it came with a bottle of local wine. The restaurant wasn’t fancy, but the service was good.