The works carried out since 1999 by the French archaeological mission in Petra on the temenos of the Qasr al-Bint were complemented by a renew architectural analysis, allowed by the excavation of a peristyle building, located east of the temple (1999-2014), and the exposure of the monumental staircase of the temple itself (2015-2018). The paper integrates both the archaeological evidence and the architectural analysis of the excavated structures, presenting a revised reconstruction of the area during the Nabataean and Roman periods. We will first discuss the spectacular refurbishing of the monumental stairs with white marble in the second c. AD, displaying a rather original design; we will then develop hypothesis and reconstruction drawing concerning the second construction, a luxury Nabataean two stories building. It was centred on a courtyard surrounded by a Doric portico, supporting a Corinthian gallery at the upper level, with screen walls adorned with colonette. Beside this sophisticated courtyard, the monumental gate of the building, with imbricated Nabataean and Corinthian orders, was studied, revealing two main successive construction stages. New perspectives are light out with those discoveries