The mineral veins of the North Pennines are world renowned source of lead, but they also contain other precious metals, including silver. During the 19^th Century, the mill was a major site for smelting (a process to recover lead and silver from raw minerals). This was an area of intense industrial activity and supported a larger community than we have today. Since closure in 1896 and partial demolition in the 1980s, the mill site had become overgrown, but beneath the dense vegetation lay a Scheduled Monument of national significance. Working with the local community and heritage specialists, the AONB Partnership recovered and interpreted the smelt mill remains in 2018 and undertook an in depth investigation into the development and working of Allen Smelt Mill.

Allen Smelt Mill connects into the wider landscape of the Allen Valleys; a two-mile flue system terminates in a stone built chimney to the south west. Part of the site has been levelled and repurposed, but surviving structures today include an ore hearth, condensing chamber, bouse teams where the ore was sorted, and a central entrance point into the flue system.