Each street is ~1 mile across. The distance between two successive "streets" is ~10 miles. The whole "city" is ~100 miles measured on one edge.

I, for one, welcome our new undersea giant overlords.

P.S.: Gmaps is full of artifacts like that. Here's another one, bigger than Ireland:

http://maps.google.com/?ie=UTF8&t=h&ll=54.188155,-12...