This shed used to be called 'the Baltic' — presumably because it was so cold and draughty! Today the shed is home to Una, a 0-4-0, 61cm gauge steam engine, built in 1905 by Hunslet of Leeds. Una is a good example of the kind of steam engines working in the quarries from the 1860s onwards. Without these engines, the quarries would not have developed as they did — railway connections could make or break a quarry.

Cover Coat, Maid Marian, Wild Aster, Cloister. All named after the horses.

Una spent her working life at the Penyrorsedd quarry in the Nantlle Valley. The Museum staff have worked very hard to restore her to her former glory, and Una is now fully operational. She is steamed on a regular basis and is a splendid sight, steaming proudly along in her shiny green and gold livery.

Although a working steam engine is a romantic sight these days, in quarrying days using the engine was anything but glamorous! The drivers and stokers were expected to arrive at the quarry by about 5 am to raise steam for the day's work, and also to sort out various small problems from the previous day. The stokers would couple and uncouple the wagons, on their knees in water, mud or snow, and attempt to get wagons back on the rails by brute force. They often gave themselves hernias or lost fingers by doing so.