The twin towers of the World Trade Center — among the tallest structures in the world — were vivid, potent symbols of American culture, capitalism and technology. Their destruction, along with the horrible loss of life, leaves a collective, emotional void.

The towers — like many works of architecture in our history — acquired roles in society that go way beyond the mere functional enclosure of space.

The World Trade Center visually swept up from the shores of Manhattan, dominating its neighbors — even those with more architectural grace and finesse.

The two closely spaced towers reflected the tensions created by great economic power. They were much like a three-dimensional bar chart showing the financial strength of an organization. And they served as immense gateposts for a society holding individual liberties in high regard.

The height and girth of the towers were electrifying. Our emotional response to high objects is often a mix of seduction and fear — the heart beats faster, the senses are aroused. The notion of being on a precipice is the stuff of both exhilaration and nightmares.

Although the World Trade Center was not considered to be an exemplary piece of architecture, it was certainly a wonder of structural engineering. The clean, Spartan volumes presented a form that was easily etched into memory. They were New York City. They were the commercial cousins of the Statue of Liberty. They were icons of global power.

Though some people may not care for them, tall buildings definitely denote that a city is both culturally significant and economically dynamic.

Structures such as the Space Needle here in Seattle, the Transamerica Pyramid in San Francisco or the Dominion Tower in Toronto instantly convey a city's nature. Others — Big Ben in London or the Eiffel Tower in Paris — symbolize an entire country.

It is no coincidence that Seattle gained national and international recognition once its skyline presented a dramatically photogenic face to the world.

While we have built many prominent architectural symbols over the centuries, we have also harbored fears that they could be destroyed.

Witness the many novels and movies detailing plots to bomb or eradicate landmarks, sometimes killing thousands of people in the process. No wonder so many people commented on Tuesday that it was like watching a movie.

In real life, architectural icons have long been targeted by warring and disaffected people. For over a thousand years, churches and cathedrals were the tallest structures in many communities. As symbols of power and authority, they were often attacked. Medieval towns surrounded themselves with high walls in an effort to protect these structures.

This long-standing fascination with architecture carries with it a corresponding wariness. We subconsciously grasp how vulnerable they are to destruction — by natural forces like earthquakes and hurricanes or human actions like war and revolution.

I vividly recall watching the Russian White House on television 10 years ago as it was being shelled and set on fire during an attempted coup. In the 1930s, the Nazi Party burned down the Reichstag in Germany, a symbol of a democratic government.

In our national history, the Capitol building was burned by British troops in the early 1800s. The notion of capturing or destroying prominent symbols of culture has had a long and dark history.

The ramifications of Tuesday's attack will likely weave through our communities and the buildings we work in and visit.

We will find ourselves going through checkpoints and being subjected to searches. The presence of security measures will be more obvious and perhaps even intrusive. We may have to adapt to the sight of armed security forces within and around major public buildings, as Europeans have experienced for some time now.

The design and management of buildings probably will consider new measures for personal protection, fire suppression, and exiting in the event of disaster. We will err on the side of caution.

We will not, however, likely cease building monuments. They will continue to be important, marking place and time, serving as evidence of a strong society.

Seattle, along with the surrounding region, is already acquiring a new set of symbols in works of architecture that are visually assertive. The EMP, the Central Library, the Civic Center are but just a few examples. Such buildings invite controversy and command attention.

They also will continue to represent aspects of our culture that are vital, vibrant and precious.

Mark Hinshaw is director of urban design for LMN Architects and a regular contributor to The Seattle Times.