In the professional field of Architecture and Urban planning we can hear three common sayings : "Atmosphere is a lot of hot air", "Atmosphere is of secondary importance", and "Atmosphere is a luxury, an aesthetic surplus". The conference wonders about these three sentences and from that moment on improve the ontological nature of atmosphere or ambiance. This conference is trying to prove that atmosphere is of primary importance, atmosphere is basically a question of aesthetics and the aesthetic of atmospheres is also an ethos.