Grognet’s design was based on that of the Pantheon of Rome. Due to debates and doubts regarding the design, the first stone took till 30 May 1833 to be laid. The Rotunda has a diameter of 55.20 metres on the outside and 39.60 metres on the inside. The main façade faces south and has six columns in the Ionic style. On each side a steeple rises from the façade. Following the front elevation, the church has an analogous style at the back, but without steeples. The dome was built on the principle of the catenary profile, meaning that each stone was laid over the one underneath it.