I have been unable to identify just what Twain is referring to in this
passage from The Innocents Abroad.  He describes passing under the
frowning fortress with a garrison of one.  He calls this fortress
Malabat.  I can find no reference to such a fortress in my Google
searches (even duckduckgo).  The closest I can find is the Moorish
Castle at Gibraltar but the dates are wrong for a match.  It also does
not seem to lie on a route between Gibraltar and Tangier.  Help with
identifying just what fortress he was referring to would be greatly
appreciated.
-- 
 There are more things in heaven and earth, Horatio, than are dreamt of
                          in your philosophy.
                        http://bscottholmes.com