[quote=@Sublimation]
<Snipped quote by poog the pig>

Yeah it's like a pathway in the environment where prana flows. They arent super useful though. However fallen leylines are small spots where many leylines intersect and are huge amount of energy. The spot where a fallen leyline is also is where the holy grail cup is formed. 

In Fuyuki city, there were fallen leylines at the assmebly building, Tohsaka house, Ryuudou temple, and Matou house. 
[/quote]

Yeah, more likely than not a fallen Leyline is located at the center of Odal valley, under the mana-lab. Thanks for that.