On the subject of Wal-Mart in Mexico, you can read this story about the location of Wal-Mart’s newest store in the Mexico City area.
You can also take a look at the view from the pyramid of the sun at the archeological site.
And take a look at a picture of the new store. That link discusses the store’s history.
And here’s a picture of the relative position of the store to the archeological site. It seems to be not too close, though it will be visible from the tops of the pyramids. They did, however, disturb some ruins in the process of developing the site.
On the store’s website, they seem to defend their position by posting pictures of even uglier stores in the area.
and…