Only putting this here due to lack of space elsewhere. The castle is doubtless on an islet. But this doesn't make "islet" a valid translation of "saliente". And a salient (noun, as opposed to salient, the adjective) doesn't refer to a vertical projection, but a horizontal one - which doesn't mean it can't also stick up ...
Here is a definition of salient (n) - both military and geographical:
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Salient may refer to:
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Wiktionary, the free dictionary.
Peninsula-like salients of political geography and Military Science.
Salient (military), a battlefield feature that projects an attacker's lines into enemy territory in such a way that the attacker is surrounded on three sides.
Salient (geography), part of a discrete territory projecting out of the main portion, bordered by foreign territory on three sides, into which it projects. These are also frequently called panhandles.
http://en.wikipedia.org/wiki/Salient