Antonio Banderas was offered to visit the real Altamira cave, but he refused the offer. The cave has been closed to the general public since 2002 because public attendance was deteriorating the paintings. Banderas felt unfair to be granted a special permission and instead worked on the faithful replica which was built in a museum near the cave in 2001.
The movie is dedicated to José Antonio Lasheras, who was director of the Museum of Altamira since 1991 until his death on February 27, 2016 in a car accident.
The end of the movie states that the paintings have been dated to about 35 thousand years old. This is not entirely true. Some of the paintings have been redated to about this age using modern techniques (original estimates put them as much younger). However, the exceptional images of the bison were painted closer in time to the paintings in Lascaux (17 thousand years ago).
Mark Knopfler, singer and leader of Dire Straits, is the composer for the music of this film, in his first movie after A Shot at Glory (2000), 15 years ago. The same time that Hugh Hudson was absence from any film.