I'm just beginning to document my Spain travels online, but the Mesquite Cathedral was one of our favorite places to visit in Spain. For one thing, it's quite beautiful. For another, it shows the incredible flexibility of this country, using a Moslem mosque and converting it to a cathedral, but protecting it's origins in architecture and ornaments.
I always deem religion to be an artifact of society--a place for like-minded people to connect. But there's also the spiritual part that has been witnessed in brain activity although not well understood.