The execution of Cumbernauld New Town was certainly an exceptional representation of town centre design and a fascinating case that converges between modernist’s utopia realisation and typical town planning context. Its a plan shows great ambition to a Utopian modernization and also an aspiration to a complex energy-efficient, technology-dependent mega-structure. Though the project received much admiration and praise at that time, it soon becomes a disappointment of Great Britain, deteriorated in a shabby status. This paper examines the genesis, expansion and reassessment of the bizarre structure. It consists of three main parts. Firstly, it provides the conceptual background of regarding the Central Area as a mega-structure developing strategy and examines the challenges post for Cumbernauld. The second part discusses why the Cumbernauld evolved into its chosen form and evaluate the structural deficiency of this mega-structure. The last part points out the difficulties when consider both ‘density’ and ‘mobility’, and analyse the deficiency in vehicle separation – the solution adapted to facilitate movement in a complex structure. The paper points out the design failures and the lacking of adequate political choice during the town planning and further discuss the essence of quality urban life. The end of the second world war has stimulated Europeans countries to carry out numerous post-war planning strategies with a modernistic approach to architecture with the aim to recover and rebuild from the war. In the context of Britain, many new towns were developed following the New Town act of 1946. Cumbernauld Town centre, a brutalist modernism megastructure executed by powerful local political leaders and dominant town planner, was regarded as a creation to the outgrowth of the central government, an continuation of the regional housing movement. Ambitiously, planners intended to have the new town developed in five phases. The failure of Cumbernauld was partially due to the discourse over the question of what is the essence of physical setting for urban life – from functional planning to urbanity, the fundamental value of modern urbanism changes substantially in the 1970s. Just before the second phase, Cumbernauld was still grounded with rationalistic functional planning and a community version of the town. The ideal of ‘community’ was soon replaced by the emphasis on a further utopia idea, ‘mobility’, inspired by American consumerism. Cumbernauld was the first complete version of megastructure that was even to be realised at that time. Unlike other agglomeration -buildings completed in the 1960s, Cumbernauld was not limited only to a small range of functions but has everything needed for an urban living complex. Given that the town was to be seen as a single entity with all infrastructures needed for urban living, it is crucial to make the town centre easily accessed and well connected. Huge Wilson, the chief planner of this project, solely aspired to design a pedestrianised town with a ‘nucleated and compact settlement’, completely neglected geological constraints of his chosen site, Cumbernauld Hill. The site’s narrow and elongated nature has post constraints on the disposition of both roads and buildings. Residents heading to the town centre would have limited and constrained road of access through its stiff gradients on the way and rather than a more uncontrolled disorientated journey of exploration. The structure of Cumbernauld city centre shows no consideration about local climate but rather a blind pursuit of brutalism ideology. The avant-garde designers in 1950s advocate a new mass-housing type of terraced houses in order to achieve large complex structure. Mostly for this new household type, Clusters of distinct but subordinate parts were joined, with terrains that created multilevel podium which encourages various activities. Barbican Centre in London, for instance, has its residential “terrace” blocks being linked by high-walks and podiums and three tower blocks that stand above the podium, together, they created open space that encourages pedestrian circulation.With similar ideas of pedestrianising deck-access groups and podiums in a brutalism type architecture, Cumbernauld has a totally different structural approach. Cumbernauld rejected tall tower blocks and created groups of medium height deck access groups compacted into a jagged mound-like mega-structure. Additionally, this mega-structure contains all public amenities that real cities should have in the centre. However, it was built in the form of reinforced concrete skeletons infilled with spaces that functions as a library, shops and civic offices – a structure that was favoured among brutalism. All decks along the shops are perforated and penetrating in this “inside-out” structure, with the south-west to north-east lineation facing the direction of the strong wind. The strong and frequently rain-bearing wind was worsened in this uphill site with no other development project around. Moreover, these perforated decks that stretched along the “citadel-like structure” also resulted in narrow and limited views out of and through the centre. It is crucial for a mufti-functional mega-structure to have permeable sight and flexible viewpoints, Barbican Centre achieved that by exposing large areas of a garden in the centre of the estate. Cumbernauld, in contrast, would have narrow bands of development with contentiously changing views through the centre – a determined hindrance for its flourish as a recreational centre of town. The idea of megastructure was a solution to assist urban concentration with the assemblies of different functional groups into a compact form and to accommodate a greater mobility city by vertical segregation that allows connectivity in a three-dimensional way. The design of megastructure boils down to the conciliation of form and functions. The planning of Cumbernauld shows a disordered relationship between its served and service space. There was a complete separation of land uses. The half-mile long, multistory building contains all the facilities needed for the entire town, but only in its town centre, besides the centre, the city was completely residential. There were no primary or secondary service spaces in any other parts of the town to support the large residential groups. a highway, spanned by bridges for pedestrians, made up the megastructure’s spine, forming the main vehicle routes. Pedestrians were to use a system of winding pathways and threatening dark tunnels among the standardised array of houses to find its way to the centre. Though the town centre was designed to be within walkable distance, few would have enjoyed living here when wherever they turn, they saw the same tastelessly disorientated regimentation of residential housing. The designers adopted a most unpractical and extreme way to reconcile ‘density’ and ‘mobility’ – by completely separating pedestrians and vehicles. The decision to set the town centre on top of the ridge toughened the already challenging transportation planning. Vehicle-pedestrian separation was to be designed into the core of the new town, in a way that both urbanity and mobility would be satisfied. The primary idea of creating a unified mega-structure with facilities and services concentrated in the town centre has defined its large and dominant structure, simultaneously the unprecedented demand for vehicles has also made horizontal separation impossible. Vertical stratification was introduced. This infantile transportation planning created a ‘forced circulation’ system with no crosswalks and only numerous overpasses and underpasses for pedestrians. In fact, The proposal of the traffic-separated system was not new, as seen in Antonio Sant-Elia’s Manifesto of Futurist Architecture, and more recently, Le Corbusier’s Unite Habitation and ideal city. Marseilles at Park Hill in Sheffield and the Golden Lane project in London both provide practical attempts of the traffic-separated system and deck-accessing housing. Despite this example, Cumbernauld fails to succeed any of them. The megastructure of concrete skeletons with flat roof already proved unsuited to the Scottish climate, the town centre which deteriorated over time had also made the labyrinth of pathways obsolete. Together, this ‘self-supported’ system of megastructure created a vicious circle of an inhospitable condition, which further leads to an unmitigated failure. Admittedly, the failure of the Cumbernauld was not only due to its structural and functional complications. The entire planning of the project was lead by different groups that show inconsistency about both design intentions and methodology. Much effort was made to correct design faults in order to improve the living conditions of user groups in the latter stage but yet proved to be ineffective. It is without a doubt that Cumbernauld was the first-ever bold attempt to reconcile modernism and town planning in the brutalism ideology. It reminds us about the responsibility of recognising the underlying complexity between modernism and city planning, and megastructure is not a means to resolve the conflict when other formulae for attractive town design should be produced base on different environmental and cultural concerns. Nevertheless, the Cumbernauld New Town shows respects for Corbusian ideals, though failed, it was a ambitious attempt and a failure worth remembering.