As an example of how the cities of the region have merged after the 1978 reforms, these images are a closer look at Guangzhou and Foshan. Even in 2000, they were clearly separate cities. The land between them then fills in with urbanization.
The 2017 image shows the appearance of what appear to be several black dots between the two cities. These are high-rise residential buildings. They look a little similar to the fish ponds, but these are a bit smaller, and they are dark because of the shadows they cast on the ground.