For all you geology aficionados, this new attraction in south-eastern Spain may attract you! It was located in an abandoned mine 20 years ago, south of Cartagena, and is opening to the public on August 5th, after many years of construction work to make the site safe/accessible to visitors.
The experience costs €22 per person, and consists of a group tours of a maximum of 12 visitors through the massive geode. Some sections of been described as "underground cathedrals", that reach a height of up to 40 meters! There is also evidence the some of the transparent lapis was mined here in ancient times and then used to construct windows of some nearby Roman Villas.
Here is the article (in English), from one of our national news papers: https://elpais.com/elpais/2019/07/30/inenglish/1564499931_206119.html