Here's a fun technique for taking your skyline photos full circle. With this technique, the center of the photo will be filled with sky and buildings will circle the edge. Here are the steps to creating the look in Photoshop or Elements:
Select a Skyline photo to work with. Here are a few tips for choosing a photo:
Choose a picture with a strong horizon line.
The right and left edges of the photo should be reasonably similar.
A photo with a lot of clear sky is easier to work with. You can choose either a day or night photo.
Don't be afraid to crop a photo to make it work.
Open the photo in Photoshop or Elements.
If the horizon line is not straight, crop and straighten it.
Select Filter > Distort > Polar Coordinates.
Tick the button next to Rectangular to Polar and click OK.
Press Ctrl J (Mac: Cmd J) on your keyboard to duplicate the photo.
Drag the bottom layer to the trash can in the Layers panel to delete it.
Press Ctrl T (Mac: Cmd T) to get the transform controls and drag the side of the photo in to make the image into a circle. Tick the checkmark to confirm.
Now get the Ellipse tool and Shift while you drag out a circle that covers the portion of the photo you want to keep.
Get the Move tool and drag the circle into position over the image, then drag the circle layer under the photo layer in the Layers panel.
Select the photo layer and choose Layer > Create Clipping Mask.
Now your photo is in a circle.
If there is a noticeable seam where the edges are joined, use the Clone stamp tool or Spot Healing brush to clean up the seam. If the sky is clean, the healing brush will work fine. For more complicated skies, use the Clone stamp instead.
Finally, select both the photo layer and the circle layer and press Ctrl E (Mac: Cmd E) to merge them.