Brandon Donnelly — Daily insights for city builders. Published since 2013 by Toronto-based real estate developer Brandon Donnelly. — Page 511

This past weekend I was reminded that Phoenix is largely what it is today -- the 5th biggest city in the US -- because of two very important things.

Firstly, the city had to figure out water supply.

About 50% of the city's water supply comes from surface and groundwater, specifically the Verde River and the Salt River watersheds that are to the north and east of the city. And about 40% comes from the Central Arizona Project , which is a 541 km diversion canal that pulls water from the Colorado River and brings it through the state (terminating in Tucson). From what I have read, the CAP canal serves about 80% of the state's population.

Secondly, Phoenix needed A/C.

Air conditioning was first invented at the beginning of the 1900s, but it really didn't become ubiquitous until the second half of the century. And not surprisingly, it made the southwest of the US far more appealing. In 1950, Phoenix had just over 100,000 people. By 1960, the city had grown by about 311% to reach nearly 440,000 people. Apparently there was more construction in 1959 alone than from 1914 to 1945 combined . Air conditioning made Phoenix's summers bearable.

Air conditioning is such an interesting topic because it's one of those things that many of us take for granted. When you walk into a store or an office building in the summer, you expect it to be cool. But it hasn't really been around all that long and its invention has, in many ways, been instrumental in defining the modern city . Even something as common and banal as a glass office tower with large floor plates would not be possible/practical without air conditioning.

We can certainly debate how sustainable it is to urbanize and air condition desert climates like Phoenix, but there's no denying that air conditioning has had a profound impact on our urban landscapes. Diversion canals are pretty important too.

I have been in a few of Frank Lloyd Wright’s houses and in every case it turned out like this:

The Prairie School (of architecture), for which Wright was a pioneer, was all about horizontality. That typically meant flat roofs, deep overhangs and, in the case of Wright’s work, exceptionally low ceiling heights.

I’m about 6’3”. Many of his clear heights were less than 7’ and I believe his doorways were often 6’2”. This clearly doesn’t work for me, but it mattered for what Wright was trying to do. And I don’t think he was the type to worry about small matters like the comfort of tall people.

The above photos were taken at Taliesin West in Scottsdale, Arizona . Wright bought the land (495 acres) in 1937, and turned it into both his winter home and a teaching studio.

Apparently Wright paid $3.50 per acre at the time, which feels like a pretty good deal to me. It shows you the power of just buying and holding things over long periods of time.

Today, Taliesin West is the home base of Wright’s foundation and also a UNESCO World Heritage Site. I’m glad I was able to finally visit it after reading about it for so many years in architecture school.

A new brightly-colored rooftop installation opened up this week in Rotterdam . It includes a 30-meter-high aerial bridge that connects a few of the city's rooftops. Designed by Rotterdam Rooftop Days and MVRDV, the " Rotterdam Rooftop Walk " is designed to bring awareness to the city's rooftops and demonstrate how they might be used as an added layer of public infrastructure within the city. The installation will run from May 26 to June 24.

This is a neat idea and not just because I like bright orange things. Rooftops are, by and large, underutilized assets within our cities. It behooves us to do more (I just wanted to say behooves). But I think it's important to keep in mind that aerial bridges and rooftop spaces can come in many different forms. I think you could argue that there are aerial bridges designed to enliven forgotten spaces (like this example here) and there are aerial bridges designed as a solution to appalling and inhospitable ground planes.

Sometimes these inhospitable spaces are because of extreme climates and sometimes it is because we forgot how to design spaces that are actually enjoyable for pedestrians. The former of these two scenarios is, I guess, more excusable. But I do think that many cities lack the kind of densities needed to animate multiple layers of public spaces. Often you need to pick where you want to focus people's attention.

Still, bright orange walkways. Neat.