Catalonia has become the mecca of Motocross in Europe; here is a quick list of the circuits surrounding CDG Mx Retreat.
I grew up spending my winters road tripping around all of these circuits, and it made for the best training and family fun! I have added the Instagram handles of the circuits, as I've found this the best way to contact them.
Some have specific opening days, some will solely open just for you. Instagram combined with google maps should enable you have the best time.
8.@motocros_rufa part of MotoClub Serge-Ponts
9.@motocros_rufa part of MotoClub Serge-Bellpuig
10.@motocros_rufa part of MotoClub Serge-Rufa