Originally Posted by Hartson
I heard сlay in Rome is the most similar to RG.
No, it's faster due to surface composition: thin topsoil clay layer over asphalt.
The main courts at the Madrid venue are all indoor courts in all but name due to being surrounded by those metal "boxes". That's the crucial factor IMO, not altitude; Madrid is only c. 600 mts above sea level.
ATP Monte Carlo is the closest to RG in terms of surface and playing conditions.