This is one of the phenomena that occurs at the The Oregon Vortex. You can actually see and take pictures of the change in height, as is shown below. When you have the pictures developed you can even measure the difference in height on the pictures.
However, it is important to note that whatever instrument you use to measure with while inside the affected area you will always measure to be the same height because the instrument of measurement will change in size right along with you. So don't forget your still camera!
These pictures shows two people standing on a level platform within the area in the backyard of The House of Mystery, close to the area's center.
These pictures have the potentially confusing background lines and angles of The House of Mystery cut out. The change of height is still just as visible without the background.