This unassuming hillock marks the spot where a Mac Coghlan castle once stood, a late medieval tower house that dominated the local landscape until its destruction. Today, visitors seeking stone walls and battlements will find only earthworks; the castle's dressed stones having long since been repurposed by practical 19th-century builders.

The castle's architectural fragments found new life in nearby houses, where keen-eyed observers can spot remnants of its former grandeur. An ogee-headed window here, a single-light round-headed window there; these salvaged pieces tell the story of what was clearly a substantial fortification. The late medieval punch-dressed stones bear distinctive pock marks arranged in patterns remarkably similar to those found at Coole Castle, suggesting shared construction techniques or perhaps even the same craftsmen working across multiple Mac Coghlan strongholds.

First documented in the ITA Survey of 1942, the site has since been recognised as an important example of the tower houses that once dotted the Irish midlands. These fortified residences served as both family homes and defensive structures for Gaelic lords like the Mac Coghlans, who controlled this region throughout the medieval period. Though the castle itself has vanished, its stones live on in the walls of Streamstown, a peculiar form of architectural reincarnation that speaks to Ireland's complex relationship with its medieval past.