Initiation well

Initiation Wells in Quinta da Regaleira, Portugal. 

1. They are connected by tunnels 
2. So as to ensure uniform distribution of water

 
https://www.google.com/search?site=imghp&tbm=isch&source=hp&biw=1280&bih=600&q=Initiation+well
https://www.youtube.com/results?search_query=Initiation+well