Tr Bach (small tower) replaced the Twr Mawr as a lighthouse in 1976 with just a directional light. It has never been a proper lighthouse (due to its size) but it was build in the early 19th Century as a stone beacon to help ships transporting slate through the Menai Strait. At that time Welsh slate production was at it's boom time and they produced as much as 90 percent of the worlds slate and Penrhyn and Dinorwig slate quarries were the biggest in the world.

Twr Bach on Llanddwyn island - Newborough visitor guide showing a virtual tour of 'Twr Bach on Llanddwyn island' linked to an interactive map with local and travel information. 360° panoramas from Anglesey.