Vertical

"You know what you've got there mate, you've got Converging Verticals..."  

This is what happens when verticals go bad. You put your wide angle lens on, because you're standing in front of a large and imposing building and point the camera up to "get it all in" and out pops the old Converging Verticals. 

In a way it makes the building look like its falling over.

Equally you could argue that is what we see when we look up, so it does represent a true view. Now there are various ways to tackle this, you could buy an expensive tilt and shift lens, but that's really intended for serious students of architecture, or formal interior pictures. (Next time you look at a quality interiors magazine, check how straight the walls are...)

You can attempt to straighten the image in Photoshop, and this can be successful with small amounts of distortion, but try too hard and the results will look very wrong.

There is another method. You can stand as high as you can manage,  keep the back of the camera vertical and accept that you get a lot of foreground in the shot. If you check this blog post, you will see the picture of Canterbury Cathedral is an example of this technique.

I would suggest that a certain amount of this effect is acceptable if you are making a point about the height and space of a building, such as this picture of the Palace of Westminster. Nice straight lines from my Zuiko zoom.

However, it may be that this picture of the Cathedral in Florence has taken the lean too far.  The lines were not so straight from my old 20mm Nikkor. The crazy angles and the strong  patterns of the building do make for a striking picture however...

Finally, you can use the effect as a graphic statement. This is downtown Manhattan, quite near Wall Street. Another Zuiko wide lens shot.