I came across a couple of men doing survey work in Amsterdam.  They were measuring the subsidence of Amsterdam buildings which can result in any building to tilt or pitch in any direction.  As you walk through this city you should take special attention to detect buildings that are not lined up correctly with buildings next door.

In the image above, you can see that the near building and next building are not lined up properly due to subsidence.

In the image above, the near worker is using a survey transit to take site readings at the stick being held by the worker in the far right distance.  In the image below the worker is holding a bar code survey level rod, that rests upon a special bolt that is attached to the building.

The individual seen in the picture above places his survey level rod upon a bolt that is driven into the side of the building.

The survey level rod is placed on top of the bolt in the image above.  Not every building has this bolt, just selected buildings.

Also, there is a mirror that is mounted on the building wall just above the survey stick.

As you walk through Amsterdam, you might take note of gaps and tilting among some of the buildings.

For more information about this problem: http://earth.esa.int/fringe07/participants/559/pres_559_carocuenca.pdf