Context : HI shells and supershells , found in discs of many galaxies including our own , are formed by the activity of young and massive stars ( supernova explosions and stellar winds ) , but the formation of these structures may be linked to other energetic events , such as interactions of high-velocity clouds with the galactic disc .
The larger structures in particular significantly influence their surroundings ; their walls are often places where molecular clouds reside and where star formation happens .

Aims : We explore the HI supershell GS242-03+37 , a large structure in the outer Milky Way .
Its size and position make it a good case for studying the effects of large shells on their surrounding .

Methods : We perform numerical simulations of the structure with the simplified hydrodynamical code RING , which uses the thin-shell approximation .
The best fit is found by a comparison with the HI data and then we compare our model with the distribution of star clusters near this supershell .

Results : The best model of GS242-03+37 requires , contrary to previous estimates , a relatively low amount of energy , and it has an old age of \sim 100 Myr .
We also find that the distribution of young star clusters ( with ages < 120 Myr ) is correlated with walls of the supershell , while the distribution of older clusters is not .
Clusters that have the highest probability of being born in the wall of the supershell show an age sequence along the wall .

Conclusions : GS242-03+37 is a relatively old structure , shaped by the differential rotation , and its wall is a birthplace of several star clusters .
The star formation started at a time when the supershell was not already supersonically expanding ; it was a result of the density increase due to the galactic shear and oscillations perpendicular to the disc of the Milky Way .