A group of 18,000 year-old cave paintings has been discovered in the Basque Country area of Gipuzkoa, in northern Spain, El País reports. The paintings were found inside the Danbolinzulo cave, where a number of ceramics dating from the Bronze Age were located 35 years ago.

The breakthrough discovery was made last December. A team of experts, who were inspecting the cave, ran into a previously unseen tableau, where up to 10 animal figures, representing deer and goats, were identified.

Upon their discovery, the cave was immediately closed to the public to allow for further research. Experts are suggesting the paintings could be between 18,000 and 33,000 years old (a period known as Upper Palaeolithic or Late Stone Age), based on the red iron oxide pigments used to make them and their distinctively elongated style.

The team is now working to determine whether the paintings were all done at the same time, or at different stages. Certain similarities with other cave paintings located in the northern coast of Spain—like the ones found in the iconic Altamira cave (see Spain Will Keep Sistine Chapel of Palaeolithic Art Open to the Public)—have already been pointed out.

“The study of these newly-found paintings will open up new perspectives and provide key information about the first stages of the art of Humanity,” Marco García, Prehistory expert at the Basque Country University, told El País.