The un-built zones or "openings" in the urban fabric of cities change over time, revealing changes in priorities, circumstances and social values. Civic spaces particularly reflect transforming attitudes and commitments. The Piazza San Marco, in Venice, Italy, is a fitting example of an urban zone that has been, up to the present, a pivotal meeting place. As a central site of cultural, social and economic exchange, the Piazza has been in active use from the ninth century.

From its inception as a small apron-space in the ninth century to the thirteenth century's enlarged and ornamented civic square, how has the Piazza San Marco been used and how has it served a variety of people's interests? If examined over time, can its transforming contours and usage contribute to an historical study of how Venetians saw themselves and imagined their city relating to the larger world? What is uncovered, in the historical view of it as a civic space, is that priorities and values did change according to Venice's perceived relationship to the region and to the Mediterranean world. If the ninth century inception, eleventh century reconstruction, twelfth century expansion, and thirteenth century enrichment of the Piazza are studied, in the light of its physical amendments and its usage, it is apparent that Venetian ideas about limits, borders and boundaries are transforming.

A sense of spatial expansiveness develops, born from an increasing ease with being a water-based state, from the eleventh century on, evidenced in a redefinition of the Piazza San Marco in terms of its connection, both physically and ceremonially with the lagoon. Shifting from the ninth and tenth century concerns with the definition of perimeters and the need for defense of the lagoon, what emerges, in tandem with growing Venetian trade, is an emphasis on the Piazza representing the city-state as an imperium. Already a more amorphous entity to define because of the city being surrounded by the lagoon, it is only step away to begin to identify with more distant bodies of water. At first at ease within the Po and Brenta river networks, the Venetians expand to establish control of the upper Adriatic followed by their dominance in the entire area of the sea.

It is only a matter of time and of opportunity, before dominion is extended to a strategic chain of entrepots in the Mediterranean and mare nostrum, itself, seems an extension of the Venetian lagoon. Methods used in this study included site visits for measurement and observation and the study of archival records and chronicles. Great use was made of reports on the limited archaeological work that has been done on Rive Alto as well as the lively debate and scholarship reflected in the voluminous secondary work.