I would go for "uma paisagem suave/moderada/agradável (aos olhos)/harmoniosa (talvez com colinas, não montanhas ou aparecimento abrupto de acidentes geográficos).
That is, without steep hills, rugged mountains, irregular or craggy terrain, etc. A landscape that is not difficult to move within.
See that the antonym of rugged can be gentle.http://dictionary.reverso.net/english-s ... 0landscape
It could also be referring to a beautiful, nice place
as well, like some prairies etc.