We visited this site on the last day of a week long visit to Nevis.  It is not the most well-preserved colonial fort in the Caribbean, but there is a lot of interesting history here.  The fort is difficult to access. Unless you have a car, you need a taxi or a tour.  There is an audio tour for $10 US that is very informative, but probably overpriced.  It is also $10 US per person to enter the site.  The view is breathtaking!  It would take a few hours to wander around and see everything at a leisurely pace.