The Trancão River drains a metropolitan-scale watershed between coastal areas and limestone formations. The banks of this river have been developed over time through various stabilization efforts, including landfills, docks, and dikes, as well as periods of transgression.

The valley carved by the river along the Lisbon coastline features steep slopes and serves as a central point to the north of Lisbon, especially at the river's crossing. Although the river has become unnavigable beyond Sacavém due to the alluvial sediments deposited along its banks, the canalization of waters from Alviela and Valada, combined with urban growth in the opposite direction, has enhanced the significance of downtown Sacavém within the metropolitan area.

Cities along the coastline, both to the north and south, are connected through Sacavém, which acts as a central hub for distribution and transit in the expanding metropolis. The inland seas to the east and west illustrate a continuous landscape formation, where geological events continue to shape the organization and perception of the area today.

While the concentration of daily transportation at one point highlights the scale and importance of these suburban regions, the development of an agricultural and river park in the vast inland floodplain emphasizes the interconnectedness of the territory north of Lisbon. The Rossio of Sacavém serves as both the starting and finishing point for this network.