Around 150 buildings, many off-bounds to the general public during the rest of the year, throw open their doors, and gates for the annual Edinburgh Doors Open Day.
Doors Open Day has taken place each year, since 1991, and over the whole weekend since 2009.
Organised in Edinburgh by the Cockburn Association in conjunction with the national Doors Open Day event, the weekend features free tours, activities, exhibitions and/or talks which bring the history or everyday use of a building to life.
There is also a programme of free lunchtime and evening talks in the week running up to Doors Open Day.
Participating buildings and events vary from a roam around the Assembly Rooms to behind-the-scenes access at Festival Theatre, from enjoying views out to Fife from Corstorphine Hill Tower, to organ recitals at St Cuthbert's Parish Church.
As well as sites of historical interest, you can satisfy your inner engineer with a tour of Torness nuclear power station or Seafield Waste Plant. One provides enough energy to power around 2.2 million homes while the other treats waste water of around 850,000 people.
Venues participating in Doors Open Day vary in size from a 1933-era police box to the palatial Donaldson's building, designed by renowned Edinburgh architect William Playfair, which has recently been converted into a high-end, residential apartment complex.
Many sites organise additional free activities for children and families.
Not all buildings are open both days and many are ticketed so you should check the program for specific buildings opening times.