The French Ministry of Culture has made part of their database of historical monuments, Base Mérimée - monuments historiques, publically available to use under an Open Licence. The dataset can be obtained from the website data.gouv.fr in CSV-format. To increase the density of archaeological information in Regnum Francorum Online (RFO), a subset of the base Mérimée dataset has been integrated into the GIS, that is, monuments that correspond to the aim of RFO and attested before the 10th century AD. The external dataset at RFO contains 1719 sites (out of 43720), covering monuments in 1224 French municipalities (communes). The Base Mérimée does not contain coordinates, so georeferencing of the monuments is done at runtime by joining the base Mérimée database table with another table containing all the French communes and their administrative center point. The INSEE-code of French communes is used as the common key. This means that all monuments in a municipality have the same set of coordinates. Links to the full records at the official base Mérimée are provided, which contains additional information not part of the free edition, e.g. a very useful classification of monuments.
A problem in the selection of sites for the subset is that many records are undated, however their description indicates they belong to the period before the 10th century. Undated records described by the terms (or in a combination) vestiges, romain, archéo[-logique], amphithéâtre, oppidum, anciens, antiques, borne milliaire, dolmen, tumulus, menhir, [paléo-, méso-, chalco-]lithique have also been selected. The Base Mérimée datset is implemented as its own geographical layer, and as additional information of French places in RFO. Click the link to load the layer at RFO, and from there, click the symbols on the map to see a list and description of monuments in the selected municipality.
The French Wikipedia community has started to author articles, one for each monument, using the information from Base Mérimee as a starting point, see further Monument historique (France) at the French Wikipedia. Quite a number of monuments are also individually georeferenced.