Mbanza-Ngungu was once a colonial resort. There was a grand hotel called the Cosmopolite which is now roofless and crumbling, used as a communal clothes drying area. I wasn't allowed to take a picture. There are old villas too, perched above the valley.
Apparently there is an occasional train on these tracks but it's hard to believe. We glimpsed the station where rusted trains lay on their backs, wheels in the air, or on their sides grown over with vines.