These ruins are what remains of the Butler castle that, in 1698 was leased to John Carden.
The castle was originally built by James Butler, 4th Earl of Ormond.
The Carden family came from Cheshire and developed the town of Templemore. The castle where they would live in was accidentally destroyed by a fire in 1740, and is now known as The Black Castle.
The first thing that can be seen in the town park is the entrance in the bawn wall, facing southeast (110°).
Next to it, but completely overgrown, is the castle. Due to the very thick and lush vegetation, it's impossible to see anything of the building apart from the north-northwest (335°) corner.