An important historical documentary heritage is preserved in the Arxiu del Comú.
It is basically consisted up of parchments and books that bear witness to the city and country history. Thus, for example, 36 parchments dated between 1289 and 1636 are kept in the Archive.
The oldest, measuring 640x2240 mm, deals with a debate still in force seven centuries later: the boundaries between the cities of Sant Julià de Lòria and Andorra la Vella through the mountains of Forganyà and Perafita. This parchment, in addition to being the oldest preserved in the Archive, is signed by Roger Bernat III, one of the two co-princes who signed the founding document of Andorra: the Pareatges of 1278 and 1288.
The Archive also contains the books of minutes of the Common Agreements from 1579.
The troop books (accommodation of soldiers in houses in the city during times of war), of accounts, where each once a transfer of powers was made between outgoing and incoming mayors, payments and collections that had taken place during the term were recorded.
One of the most curious examples preserved is the minutes book of the Carnival Council. We can find about a century of traditions around the days of Carnival, from 1731 to 1845. This document contains the rules that had to be respected during the celebration, as well as the organization of meals and dances.
It also houses a photographic collection, with more than seven thousand images, both physical and digitized on various topics such as festivals, traditions, customs, relevant characters, urban and natural landscapes, etc.