Moria: The only place where a Nazgul was not sighted?
Well the same goes for Rauros, doesn't it? The Nazgul which steed Legolas shot, were encountered at the beginning of the Sarn Gebir some 30-40 miles north of Rauros.
or amon sul because its the only place orcs weren't
That goes for Edoras as well... Dunledings are not orcs.
HINT: Connect a single caracters actions at the sites (or very close by), and see where that brings you