90943
The middle stretches of the river have many limestone caves which were inhabited by humans in the prehistoric era ; the caves are several types of limestone formations , namely tuffeau ( a porous type of chalk , not to be confused with tufa ) and Falun ( formed 12 " million years ago ) .
 Falun
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 Falun