The Basilica of Maxentius in Rome features the largest opus caementicium vaults known to have been constructed in the Roman Empire. The present paper presents a structural reconstruction of the building and initial stability analysis of its original geometry. The barrel vaults and groin vaults are analysed, together with the stability of the supporting and buttressing elements. This initial study yields that the original construction was stable. However, two of the three naves of the Basilica have collapsed and further study will be necessary for determining the causes of such structural failure.