Doors Open Days promotes architecture and heritage sites to a wider audience within and beyond the country's borders.
It is an opportunity to discover hidden architectural gems and to see behind doors that are rarely open to the public for free.
This joint initiative between the Council of Europe and the European Union aims to give people a greater understanding of each other through sharing and exploring cultural heritage.
Scotland is one of the few participating countries where events take place every weekend in September, with different areas choosing their own dates.
It is estimated that 5,000 or more volunteers give their time to run activities and open doors for members of the public.