Tower

http://psd.tutsplus.com/tutorials/tools-tips/useful-applications-for-the-clone-stamp-tool/
I started by opening this image in Photoshop. I increased the highlight levels of the tower. I created a new layer and renamed it "Straight Tower". I selected a clone source by pressing down the Alt key while using the Clone Stamp Tool. I drew a vertical guide and changed the offset angle to 4.0 degrees. I clicked on the "Straight Tower" layer and painted over the tower. This goes over the original tower and makes a new tower appear that is straighter. Then, I did the details around the bottom of the tower and the sky. I selected a new clone source and painted over more areas of the picture. The hardest part of this tutorial was fixing all the the detail work because it was difficult to make it look correct in the picture. The easiest part was changing the highlight levels of the photo.