The cave art found in the cave could date to 40,000 years ago which would make it the oldest cave paintings ever found.  Also, there has been symbolic art found in the cave which suggests that humans used symbols for perhaps the first time. 

Cave of El Castillo

The Cueva de El Castillo, or the Cave of the Castle, is an archaeological site within the complex of the Caves of Monte Castillo, and is located in Puente Viesgo, in the province of Cantabria, Spain.

• http://en.wikipedia.org/wiki/Cave of El Castillo
• New Scientist, v. 220, issue 2944, p. 16-40.