If you wanna know anything about the history of lourdes have a look at
This is for a lot of people a holy place, and in the history, they say, happened miracle healings after drinking and washing in the holy spring.
We didn't got a miracle healing after drinking from the holy water and washing our hands in it. Perhaps we should have had a bath in it... . The architecture is great! And so many churches (there are 4) on one small place, I think you can only find in Lourdes.
By the way: Lourdes is on the 2nd place after Paris with overnight stays in France but it's not even within the Top 100 of the biggest citys of France (Toulouse is place 4).