Adding some blur to the background adds an immediate sense of depth to any photo. You can do this in Adobe Photoshop by separating the background from the foreground objects and then adding a Lens Blur to the background.
Examine the image that you want to blur in Photoshop. Decide which parts will belong to the foreground and which should be blurred in the background. In our example here, we'll keep the front statue and all of the grass in the foreground and put everything else into the background.
Click the Quick Selection Tool in the Toolbox. This tool is usually the easiest one for selecting foreground objects — for more complicated subjects, however, you may want to use some of Photoshop's other selection tools for your photo. Adjust the Brush Size in the Options bar and drag the cursor over the foreground objects. Make sure the selection outline doesn't miss any parts of the objects. To add to a selection, click the Add To icon in the Options bar and then click the spots the tool missed the first time around. To remove parts of the photo from the selection, click the Subtract From icon in the Options bar.
Press Ctrl-C to copy the selection and Ctrl-V to paste the copy as a new layer. In the Layers panel, click the Eye icon beside the Background Layer to hide it from view. Using the Tool Box's Eraser Tool, erase any portions of the background that might have been included in the background.
If your selection is missing any details in the foreground, delete the copied layer in the Layers panel, select Reselect from the Select menu and then add those missing portions with the Quick Selection Tool.
In the first layer, lick the Filter menu and select Blur or Blur Gallery to choose the best filter for your photo. To make the photo appear as if it was taken a camera using a wide aperture, select Lens Blur from the Blur options. To give the appearance of motion, select Motion Blur. If you're not familiar with blurring options and styles, like Tilt-Shift or Gaussian Blur, read the tutorial on applying Photoshop Blur Filters.
Adjust the Blur filter settings to achieve the result you need. In the Lens Blur settings, select the iris shape from the Shape menu. To smooth the iris' edges, drag the Blade Curvature slider to the right. To rotate the iris, drag the Rotation slider. Drag the Radius slider to increase the amount of blur. Experiment with the other settings, like the Specular Highlight Brightness and Threshold, or by adding Noise to the blur.
Before clicking OK, change the Preview option from Fast to Accurate to see how it will look. Note that Accurate previews can take up to a minute to be generated, depending on the photo size and your computer's speed.
Examine your image closely by zooming in and out. To reduce the amount of blur, select Fade Blur from the Edit menu and then drag the slider as needed. To undo the blur and start again, press Ctrl-Z.