Sorry, that's where GMaps put the center of Pilsen. I can update the link if you want... =)
(ObGmapsWeirdThing: My wife and kids were outside on the driveway when the google cameras went by. Now I can see them all the time, staring back at me with their blurred faces...)
These are the signs by my wife's office - it's really hard to visualize but at points in the sidewalk there are grates that you can see through down to the old sidewalk below
http://goo.gl/maps/OlFm7
You can see where the sidewalks enter on the second floor of these flats and the original ground level entrance is now below street level.
We had lots of fun goofing around in the "cave" down on the first floor.