What to call a river harbor?
What would you call a place where several boats are kept on a river? "Harbor" sounds wrong to me, as I associate it with the sea.
Here is an example of such a place in Brazil, from this Google Street View photo sphere:
I'd describe this as a moorage.
A place where a ship or aircraft may be moored
Other options would be mooring
a place for mooring a vessel
(boat) landing (area) (as suggested by @Xanne)
and
port, which can refer to the part of town where boats are moored.