It might be a blot on the Peak District National Park, but its one of the areas biggest employers and 2,000 people were keen to see inside it on its 85th birthday.
Hope Works, operated by Hope Construction Materials, is the largest cement manufacturing operation in the UK, producing 1.5m tonnes a year.
Visitors were shown the quarry and works and travelled on a steam train which connects it with the main Hope Valley line.
Bosses also laid on stilt walkers, face painting, donkey rides, a historical exhibition and music.
Industrial director Ashley Bryan said: “We weren’t lucky with the weather but the event was a big success, we had lots of positive feedback and we are delighted that so many people came along to help celebrate our milestone.
“August was a boom month for the growth of construction in this country. The Open Day gave Hope an opportunity to reinforce its role in both economic growth nationally, and in the local economy of the Peak Park.”