What a difference two years can make, especially when you're getting ready for the world's biggest sporting event: This before-and-after slideshow features satellite imagery of London's Olympic Park, the central site for the 2012 Games.
We're presenting the scene as two separate pictures, showing the north and south side of Olympic Park. In each picture, the view on the left was captured by the GeoEye 1 satellite on Sept. 21, 2009, from a height of 425 miles (684 kilometers). The same satellite snapped a picture of the same place on Aug. 3, 2011, and that's what you see on the right side of the screen.
Move the slider at the bottom of the picture to the left or the right for a full comparison of the views, or use the "See Before" and "See After" to switch between the views.
The first image in the slideshow shows the northern end of the park: There's been a lot of work done on the International Broadcast Center, the structure with a light-colored roof on the left side of the screen. The Handball Arena is the smaller, squarish building to the south of the media center in the 2011 photo.
The white-roofed, blocky building on the right side of the River Lea is the Basketball Arena, which didn't exist in 2009. Farther to the right, the Olympic Village is taking shape, just to the north of the Stratford International rail station.
The 2011 view still shows a bare spot on the left side of the river where the Hockey Center will go, but lots of progress has been made on landscaping.
The second image shows the southern end of the park, highlighted by the Olympic Stadium, where the opening and closing ceremonies will be conducted. On the right side of the screen, you can see how much work has been done on the rounded-roofed Aquatics Center and the Water Polo Arena just to the north.