The original Map IV shows four great mountain ranges, arranged symmetrically across Middle-earth: the Blue, Red, Grey and Yellow Mountains. The mountains associated with Cuiviénen are marked as the northeastern range, the Red Mountains. That term never appears in The Silmarillion, but there is a reference there to a range known as the Orocarni near Cuiviénen. Orocarni is Elvish for 'Red Mountains', so the map above assumes the two terms are equivalent, and uses the later form. (Of the other three great ranges, the Blue Mountains in the northwest survived to appear in The Lord of the Rings, but the Grey and Yellow chains in the south disappeared into obscurity.)

Tolkien's original map shows no rivers or streams of any kind. However, The Silmarillion tells us that 'Many waters flowed down thither [to Cuiviénen] from heights in the east...' (Quenta Silmarillion 3). Accordingly, several streams or rivers have been added to the map, though it should be noted that the number and location of these is purely speculative.

The old Map IV shows the Sea of Helcar as essentially a regular ellipse, with Cuiviénen on its eastern shores. However, The Silmarillion says that there was a bay in the Sea at Cuiviénen's location. While there are no bays or inlets marked on the original Map IV, then, a shallow bay has been added in the version shown above.