Visitors to the tour, which has sold out, will be able to explore the first floor of the medieval castle, cellars, and the 18th century prison cells.
Inspector of ancient monuments at heritage organisation Cadw, Rick Turner, said: "We have owned the ruins of the castle since 1961 and over the past year there has been a lot of co-operation between Swansea Council and us to realise the potential of the building and the area as well.
"We are confident in opening up the castle on Friday and I am sure if it is successful, there will be more events like it. There is an awful lot of building here to see."
Click here to read this article from the South Wales Evening Post
