Whilst the castle itself has vanished without leaving any visible surface traces, its location has been a source of confusion on historical maps for nearly two centuries. The 1838 Ordnance Survey six-inch map marks what was believed to be the castle site, though local historian O’Flanagan noted in 1933 that no physical remains could be found at this spot.

Adding to the mystery, later revisions of the Ordnance Survey maps, both the six-inch and twenty-five-inch editions, appear to have plotted the castle at an incorrect location entirely. Archaeological research has since determined that the actual castle site lies a short distance west of where it was originally marked on the 1838 map, rather than at the revised position shown on later editions.

This cartographic confusion serves as a reminder of how Ireland’s medieval landscape has changed over time, with many castles and fortifications disappearing so completely that even their precise locations have been lost. The Archaeological Inventory of County Offaly, published in 1997 and subsequently updated by researcher Caimin O’Brien, has helped clarify the true position of Tulla Castle, though visitors to the area today will find only empty fields where this defensive structure once stood.