View from the grandstand set. The black area is prepared to be replaced with a matte painting. 

Final composite of the matte painting and the running horses on the opposite side of the track. 

Original plate. For this it was required to do a matte painting of a typical roofed bridge over the river. We also had to create a wet look because a CG rain was to be comped in the shot. 

Final composite of the bridge and the puddles on the ground.