Imagine that when you walked
in here this evening,

you discovered that everybody in the room
looked almost exactly the same:

ageless, raceless,

generically good-looking.

That person sitting right next to you

might have the most
idiosyncratic inner life,

but you don't have a clue

because we're all wearing
the same blank expression all the time.

That is the kind of creepy transformation
that is taking over cities,

only it applies to buildings, not people.

Cities are full of roughness and shadow,

texture and color.

You can still find architectural surfaces
of great individuality and character

in apartment buildings in Riga

and Yemen,

social housing in Vienna,

Hopi villages in Arizona,

brownstones in New York,

wooden houses in San Francisco.

These aren't palaces or cathedrals.

These are just ordinary residences

expressing the ordinary
splendor of cities.

And the reason they're like that
is that the need for shelter

is so bound up with
the human desire for beauty.

Their rough surfaces
give us a touchable city.

Right? Streets that you can read

by running your fingers
over brick and stone.

But that's getting harder to do,

because cities are becoming smooth.

New downtowns sprout towers

that are almost always
made of concrete and steel

and covered in glass.

You can look at skylines
all over the world --

Houston,

Guangzhou,

Frankfurt --

and you see the same army
of high-gloss robots

marching over the horizon.

Now, just think of everything we lose

when architects stop using
the full range of available materials.

When we reject granite
and limestone and sandstone

and wood and copper
and terra-cotta and brick

and wattle and plaster,

we simplify architecture

and we impoverish cities.

It's as if you reduced
all of the world's cuisines

down to airline food.

(Laughter)

Chicken or pasta?

But worse still,

assemblies of glass towers
like this one in Moscow

suggest a disdain for the civic
and communal aspects of urban living.

Right? Buildings like these are intended
to enrich their owners and tenants,

but not necessarily
the lives of the rest of us,

those of us who navigate
the spaces between the buildings.

And we expect to do so for free.

Shiny towers are an invasive species

and they are choking our cities
and killing off public space.

We tend to think of a facade
as being like makeup,

a decorative layer applied at the end
to a building that's effectively complete.

But just because a facade is superficial

doesn't mean it's not also deep.

Let me give you an example

of how a city's surfaces
affect the way we live in it.

When I visited Salamanca in Spain,

I gravitated to the Plaza Mayor

at all hours of the day.

Early in the morning,
sunlight rakes the facades,

sharpening shadows,

and at night, lamplight
segments the buildings

into hundreds of distinct areas,

balconies and windows and arcades,

each one a separate pocket
of visual activity.

That detail and depth, that glamour

gives the plaza a theatrical quality.

It becomes a stage
where the generations can meet.

You have teenagers
sprawling on the pavers,

seniors monopolizing the benches,

and real life starts to look
like an opera set.

The curtain goes up on Salamanca.

So just because I'm talking
about the exteriors of buildings,

not form, not function, not structure,

even so those surfaces
give texture to our lives,

because buildings
create the spaces around them,

and those spaces can draw people in

or push them away.

And the difference often has to do
with the quality of those exteriors.

So one contemporary equivalent
of the Plaza Mayor in Salamanca

is the Place de la Défense in Paris,

a windswept, glass-walled open space

that office workers hurry through

on the way from the metro
to their cubicles

but otherwise spend
as little time in as possible.

In the early 1980s,
the architect Philip Johnson

tried to recreate a gracious
European plaza in Pittsburgh.

This is PPG Place,

a half acre of open space
encircled by commercial buildings

made of mirrored glass.

And he ornamented those buildings
with metal trim and bays

and Gothic turrets

which really pop on the skyline.

But at ground level,

the plaza feels like a black glass cage.

I mean, sure, in summertime

kids are running back and forth
through the fountain

and there's ice-skating in the winter,

but it lacks the informality
of a leisurely hangout.

It's just not the sort of place
you really want to just hang out and chat.

Public spaces thrive or fail
for many different reasons.

Architecture is only one,

but it's an important one.

Some recent plazas

like Federation Square in Melbourne

or Superkilen in Copenhagen

succeed because they combine old and new,

rough and smooth,

neutral and bright colors,

and because they don't rely
excessively on glass.

Now, I'm not against glass.

It's an ancient and versatile material.

It's easy to manufacture and transport

and install and replace

and clean.

It comes in everything
from enormous, ultraclear sheets

to translucent bricks.

New coatings make it change mood

in the shifting light.

In expensive cities like New York,
it has the magical power

of being able to multiply
real estate values by allowing views,

which is really the only commodity
that developers have to offer

to justify those surreal prices.

In the middle of the 19th century,

with the construction
of the Crystal Palace in London,

glass leapt to the top of the list
of quintessentially modern substances.

By the mid-20th century,

it had come to dominate
the downtowns of some American cities,

largely through some
really spectacular office buildings

like Lever House in midtown Manhattan,
designed by Skidmore, Owings and Merrill.

Eventually, the technology
advanced to the point

where architects could design
structures so transparent

they practically disappear.

And along the way,

glass became the default material
of the high-rise city,

and there's a very
powerful reason for that.

Because as the world's populations
converge on cities,

the least fortunate pack
into jerry-built shantytowns.

But hundreds of millions of people
need apartments and places to work

in ever-larger buildings,

so it makes economic sense
to put up towers

and wrap them in cheap
and practical curtain walls.

But glass has a limited ability

to be expressive.

This is a section of wall framing a plaza

in the pre-Hispanic city of Mitla,
in southern Mexico.

Those 2,000-year-old carvings

make it clear that this was a place
of high ritual significance.

Today we look at those and we can see
a historical and textural continuity

between those carvings,
the mountains all around

and that church which is built
on top of the ruins

using stone plundered from the site.

In nearby Oaxaca,
even ordinary plaster buildings

become canvasses for
bright colors, political murals

and sophisticated graphic arts.

It's an intricate, communicative language

that an epidemic of glass
would simply wipe out.

The good news is
that architects and developers

have begun to rediscover
the joys of texture

without backing away from modernity.

Some find innovative uses
for old materials like brick

and terra-cotta.

Others invent new products
like the molded panels that Snøhetta used

to give the San Francisco
Museum of Modern Art

that crinkly, sculptural quality.

The architect Stefano Boeri
even created living facades.

This is his Vertical Forest,
a pair of apartment towers in Milan,

whose most visible feature is greenery.

And Boeri is designing a version of this
for Nanjing in China.

And imagine if green facades
were as ubiquitous as glass ones

how much cleaner the air
in Chinese cities would become.

But the truth is
that these are mostly one-offs,

boutique projects,

not easily reproduced at a global scale.

And that is the point.

When you use materials
that have a local significance,

you prevent cities
from all looking the same.

Copper has a long history in New York --

the Statue of Liberty,

the crown of the Woolworth Building --

but it fell out of fashion for a long time

until SHoP Architects used it
to cover the American Copper Building,

a pair of twisting towers
on the East River.

It's not even finished

and you can see the way
sunset lights up that metallic facade,

which will weather to green as it ages.

Buildings can be like people.

Their faces broadcast their experience.

And that's an important point,

because when glass ages,

you just replace it,

and the building looks
pretty much the same way it did before

until eventually it's demolished.

Almost all other materials
have the ability

to absorb infusions of history and memory,

and project it into the present.

The firm Ennead

clad the Utah Natural History Museum
in Salt Lake City in copper and zinc,

ores that have been mined
in the area for 150 years

and that also camouflage the building
against the ochre hills

so that you have a natural history museum

that reflects the region's
natural history.

And when the Chinese
Pritzker Prize winner Wang Shu

was building a history museum in Ningbo,

he didn't just create
a wrapper for the past,

he built memory right into the walls

by using brick and stones and shingles

salvaged from villages
that had been demolished.

Now, architects can use glass

in equally lyrical and inventive ways.

Here in New York, two buildings,

one by Jean Nouvel
and this one by Frank Gehry

face off across West 19th Street,

and the play of reflections
that they toss back and forth

is like a symphony in light.

But when a city defaults to glass

as it grows,

it becomes a hall of mirrors,

disquieting and cold.

After all, cities are places
of concentrated variety

where the world's cultures
and languages and lifestyles

come together and mingle.

So rather than encase all that variety

and diversity in buildings
of crushing sameness,

we should have an architecture that honors
the full range of the urban experience.

Thank you.

(Applause)