Odd, I'm pretty sure it was showing +20% for the pyramids.. I'll rebuild it and check out the info.
"Reduces the cost of Library technologies and unit upgrades. Cannot be attacked. Once a day you may collect bonus gold."
Hitpoints: 3000
Can't remember 100% sure how much it reduces, but pretty sure it was 10% lower.
Also it gives 10000 gold to take from it with a 24h cooldown.
Cheers!
Notre Dame gives exactly —10% research price for troops and technologies in the library. Also it gives you additional +10000 gold in each age you advance:
Classical age: 10.000 per day
Medieval age: 20.000 per day
Gunpowder age: 30.000 per day
Enlightment age: 40.000 per day