Organised by the Ministry of Culture and National Heritage, the campaign is now in its 15th year.
This year's theme is "Step into History."
The participating sites include the Royal Castle in Warsaw and Wawel Castle in the southern city of Kraków.
The Royal Castle in Warsaw. Image by Dariusz Staniszewski from Pixabay
The historic Wawel Castle in Kraków, southern Poland. Image by Peter Tóth from Pixabay
The other two are Wilanów Palace, a former residence of King Jan III Sobieski, and the Royal Łazienki Museum, both in Warsaw.
Warsaw's Wilanów Palace, a former royal summer residence that is now a major tourist attraction. Photo: Chichebombon, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons
Warsaw's iconic Royal Łazienki Park is a tourist draw and a popular cultural venue in the centre of the Polish capital. Image by Henryk Niestrój from Pixabay
Visitors can explore the residences' historic interiors and permanent and temporary exhibitions free of charge throughout the month.
The programme also includes guided tours, workshops and museum lessons.
The Free November campaign aims to make museums and other cultural venues more accessible to the public.
(ab/gs)
Source: IAR/PAP, polskieradio24.pl, gov.pl
Click on the audio player above for a report by Agnieszka Bielawska