Historical records from the early 20th century describe several castles that once dotted the townscape, though pinpointing their exact locations has proven challenging for modern historians. One particularly intriguing structure stood beside the bridge on Bridge Street, where the Adelphi Hotel and former dispensary now stand. These buildings, which still occupy the site today, may well contain medieval fabric within their walls; the dispensary presents as a modest two-storey structure, whilst the adjoining Adelphi House rises three storeys with its three-bay façade.

The Civil Survey of 1654-6 provides tantalising clues about this castle’s history, describing it as ‘a waste castle on the gate called the gatehouse, 18 foot square’ on Corporation Land. This structure appears on a Down Survey map from 1655-6, positioned on the western side of the street just south of the bridge. The castle’s story becomes even more intriguing when examining a 19th-century sketch from the Miller/Robertson collection, which depicts a tall rectangular building, three storeys with an attic, standing prominently above its neighbours on the bridge’s southern side. This may have been the original castle, later remodelled with contemporary windows and roofing to serve new purposes.

The transformation of these medieval defences into modern buildings reflects a common pattern throughout Irish towns, where ancient stonework was pragmatically incorporated into later structures rather than demolished. Historian Conor Manning has suggested that the gatehouse castle mentioned in the Civil Survey likely corresponds to this location, making the current buildings on Upper Bridge Street potentially significant repositories of Callan’s medieval past, their modern facades concealing centuries of architectural history.