Situated on the north slope of the mound of Mareil-en-France, the village dominates the valley of Ysieux. A small villa gives evidence of the Gallo-Roman presence.
The village of Jagny-sous-bois is ruined in the XIIth century during the feudal wars between the Lords of Beaumont and Clermont. Jagny goes out in the XIXth century. The village has then for Lord Charles, a count of Flanders, Raoul de Lions and Robert de Libus, Louris.
In the XVIIth century, following marriages, the territory enters the big possessions of Potter, duke of Gesvres, and lives until the revolution there.
The small village possesses for a long time a castle, maintaining in ruin. Of agricultural vocation, Jagny-undergrowth keeps some farms.
Monuments of Jagny-undergrowth :
- The church Saint Léger - XIIIème-XVème-XVIIème century :
The church, primitively dedicated to saint Barthélémy, is dedicated to saint Léger after its reconstruction. She undergoes damage during the conflicts between the Lords of Clermont and Beaumont, and during the Hundred Years' Wars and during the religion. Several times reshaped, she threatens to collapse at the end of the XXth century. Several times reshaped, she threatens to collapse at the end of the XXth century.
For that purpose, a program of rehabilitation was thrown with the cooperation of the state and of the General Council.
The rehabilitation ended in September, 2014 with the installation of the last stained-glass windows.
- The well Holy Geneviève - XVème-XVIème century :
This well in ruin is the object of a legend. A woman would have fallen in the well by going back up her bucket and would have been saved by Saint Geneviève, boss of the Parisians. Two processions commemorated this event. Saint Geneviève's relics had then gone out of the church and led to the well.
- The fountain - on 1898:
ilt by the mayor, the mister . Lejonne. This one makes build the pipe of the source(spring) to bring the drinking water in the center of the village of Jagny-sous-bois.