Anor Londo is the City of Gods. Since yo meet gwynevere and Gwyndolin and even can find the Tomb of great lord gwyn, we can asume the lords are meant with these "gods"
There is a Giant Smith in Anor Londo. In fact, probably the last Kindhearted soul left in anor londo.
We can even confirm this Giant lived there for a long time since when talking to Gough, one of the four knights of gwynn, he remembers the giant smith and hopes he is doing all right.
Oh yeah, and also Gough is a giant himself.
So what we can say is that Anor Londo was created by lord gwyn and the Lords, but they lived at least in peace with Giants, who were also welcome in anor Londo.
Some additional minor evidence is that the entrance to Anor Londo through Sens fortress is also defended by Giants aswell as Pictures of Giants Next to Humans/Lords are shown Hanging arround in the inner rooms of Anor Londo.
Is all this still a Fan theory to you?