The Nexus in the 21st Century Istanbul - Building New Living Spaces and Opportunities. City itself forms a collective human system; today system needs a complex veining to supply hectic flow. Following the needs and emerging technological capacities, belowground connection networks become invisible machines solving transportation challenges of the city. 21st century technology is capable of hiding all infrastructure; networks started to disappear underground that made them invisible that gave way to a better controlled and clean urban form. More then that, underground connection hubs become present-day cathedrals fostered with facilities like shopping and thematic esplanades. Underground machine becomes the essential organ of the urban system. In Yenikapı, infrastructure is ideal in terms of functional rapport yet what’s missing was the articulation of the urban space; as a method of styling the joints in between the formal elements, architectural design was the major requirement to build the relation; city space is expected to extend from surface to subsurface, and vice versa. Avoiding imposing an icon, the structure is not aimed to perform a dominant attitude; on the contrary, the structure is considered as one of the elements in building the space. Main projection has been that objects of urban living integrate seamlessly with sunken public piazzas of the Center, being its coupling interface with the city. Yenikapı becomes nexus of all underground connections related to the city surface smoothly in the course of the lower piazzas created under a semi-permeable roof system. The fragmental form of the roof is derived from the complex and integral structure of the big machine; its perforated plates mimic the outlines and impressions of Istanbul. The roof is at the street level, and becomes an extension of the urban fabric as an aesthetic inkling before joining in the underground flow. The protecting shield designates the space; the permeable elements, with three-dimensional effect, filters the daylight into the sunken piazza that creates a holly vision, beside the feeling of spaciousness, exploring new possibilities of contemporary temples where people meet. An enclosure with “holes” on top, oozing beams through, is open to the intersections of energy where the ritual of mobility takes place every day. The piazzas will be enlivened with cafes, catering and shopping facilities as an extension of the street level. The atrium is flanked by semi-open alleys for flâneurs. To provide a rain and windproof interior, glass walls installed where necessary, that grants climate comfort, without obstructing the visual transitivity. A number of roof plates designed as green roofs that function as urban terraces open to sea view. The passer-by’s or the stroller’s curiosity is first piqued by the display units of the City Archive, located in the piazza; challenged with the first encounters at this strata, one may choose to become a stalker towards the Archeopark and the main expedition area that is designed as the site museum. In the same courteously manner, the units of exhibition is stretched towards the Archeo-park area, preserving the street level building relation. The museum is designed in relative pieces which may be consumed separately or totally in an order. The transparent walls of gallery modules link to outdoor exhibition areas or landscaped exteriors and to each other directly or via partly covered strata. Thematic permutations provide a unique journey that allows individual associations. The glass walls are open to the view of the passer-by’s as well the keen spectator’s. The main decision in the layout plan is made respecting the border of the ancient city walls; aware of the value of the archeological site, the main frame of the building policy have been progressive planning with regard to future excavations and possible findings, hence, exhibiting them “in situ” is premeditated. Ensuring the continuity, betterment of vicinity is envisaged. The only existing greenery is gained on a part of the land reclamation; in order to reduce the impact of strategic traffic in the local environment, a tunnel bypass is planned that will grant a slow local traffic and an option for a neighborhood park which would become the biggest urban park in Istanbul. With the new traffic organization, public plazas and new pedestrian paths will be generated. Converting the disused local train line into a local tramway connecting Yenikapi to the top destinations in historic Istanbul and designing the abandoned line as the pedestrian and bicycle route organized as hard landscape is one of the new strategies, promoting uninterrupted coastal use is another. By the sea, Pier formations will generate a leisure zone. A small size marina will be dedicated small boats. The enlivened pedestrian friendly shoreline will be connected up to Golden Horn. The water treatment plant will merge in the park by lowering its surrounding walls and utilizing the plant’s exterior surface by means of the park area. Immediate vicinity, Yalı Mahallesi is in the impact area. Instead of a plastic gentrification, a slow healthy transformation process, supporting the present dwellers, will be encouraged. In order to ignite betterment, only first row of buildings close to shoreline may be re-constructed, for their risky building quality. Yenikapı is not only a transfer intersection but also generator of urban motion. The development shall motivate the beautification of the environment and the coastline as well as the improvement of public areas, enriching the neighboring centers and communities. *Excavations undertaken during the application of the transportation projects, both the remains of a 1600-year-old “Theodosius Port” together with the “35 antique ship remains” of the World’s largest fleet collection and more than 10.000 archeological founding were unearthed. At the same excavation area, 8500-years-old settlements of first Neolithic age were also found.