Paul Andreu began designing the Aérogare Roissy-I in 1967 and it was inaugurated in 1974. It is a space of transit and transformation, which places people in an "in-between" state, a place of tensions exposing the individual to physical, intellectual and poetic experiences. Accessing the terminal by car through a winding network of roadways, the passenger must follow a pathway of initiation, gradually sliding towards a compact space; from light to shadows, where the limits are confused. A thick membrane of raw concrete, enclosed and inward looking, Roissy-I is one of the first airports where the facilities and usages are not laid out horizontally but rather organized vertically, within a dense and narrow frustum or truncated cone. It is an interchange where all the functional spaces are concentrated to make the path from car to plane as short as possible. Andreu added an intermediate level for transfer, sandwiched between the traditional departure and arrival levels. Transfers are accomplished via the central "crater," a genuine topological node, a cone of vision and the sole source of natural light inside the building. A restricted area, forbidden to all visitors, it is the start of the trip. This is the only place inside the terminal where the sky can be seen, the first promise of take-off and flight. By hollowing out the center of the monolith, the geometric point where everything converges and where one loses oneself, the architect made this not only a space of circulation, crossing the void in a straight line, but also a poetic one, an allegory of air travel and of ascension towards the sky.