This month the doors to many places you don't normally get to see are being unlocked. It's part of an initiative to celebrate the architecture and heritage of Wales, which gives the public access to a variety of buildings and heritage sites across the country.
Rob Shelley visited Llanberis' old quarry hospital to find out more.
A former WWII camp for prisoners of war is opening its doors to members of the public after being closed for around 15 years.
The 'Open Doors in Wales' scheme will see buildings that are normally out-of-bounds opened to the public.