ShiftN (Do a Google search for source links)

“Falling lines” are an often seen effect on architecture photos. This means that originally parallel lines seem to appear closer to each other on the photo. Therefore a discrepancy between original motive and later image view. With the freeware ShiftN you get an easy to use application to fix such effects with ease. Just a picture load and one button press are enought to get the automatic corretion routine running. Professional users will find additional parameters to adjust the correction intensity themselves. So this tool is a good recommendation for new and advanced users.

Works, too.

Cheers…