I have a new not-so-serious goal. I say not-so-serious because I'm busy with lots of other things and who knows if/when I'll actually get around to this. So let's just say that this goal is based on a strong interest. I would like to visit the 10 largest urban areas in the world.

I was careful to say urban areas, because largest cities can be misleading. City proper boundaries are an arbitrary measure. What matters more are the built up areas.

I have already been to a handful of them, namely the ones centered around Tokyo, Dhaka, and Mexico City. But there are more on the list that I haven't been to.

There are, however, two immediate challenges with setting a not-so-serious goal like this one. The first is that it's not easy to come up with a definitive list of the largest urban areas. It's nuanced and, for some cities, population estimates are very much rough estimates.

The second is that population figures are constantly changing. So by the time I get around to this, many of the largest cities might be in Africa (current forecast for this century) and I may be checking off the wrong list.

But let's not let perfect be the enemy of good. Here's what I came up with. And by "what I came up with," I mean that I asked ChatGPT its opinion. This is the list I got:

Then I asked the question in a slightly different way and got this list:

Then I asked it to tell me its definition of metropolitan area vs. urban agglomeration:

Finally, I asked it why Lagos, Nigeria was not on the list. Current estimates place this urban region at more than 20 million people (which would place it ahead of New York in the first list), but I don't think anyone really knows for sure. Whatever the current number, it is widely understood to be one of the fastest growing city regions in the world. This is how ChatGPT responded:

I'm a little torn because high on my list of cities to visit are São Paulo and Seoul. And they don't seem to be finding themselves on the same list. I'm also very curious to see Lagos, and I have a suspicion that it's much larger than official estimates. Regardless, there are some clearly big cities to check off. India and China would be good places to start. So I better get to work. Or not. Since this is a not-so-serious goal.

Mexico City is all kinds of big. It is the largest metropolitan area in North America, the largest Spanish-speaking city, and broadly one of the largest megacities in the world. Because of this, it can be, you know, hard to move around.

I remember visiting the city for the first time when I was in elementary school, and it standing out to me that everyone had one day of the week when they were simply not allowed to drive their car. It was/is a form of load balancing. Imagine that. (I don't know if this is still the case, or if it's even more stringent today.)

I also remember visiting the city later on, when I was in grad school, and it standing out to me that their metro had women-only cars. This was and continues to be an attempt to try and minimize the amount of sexual harassment that takes place on transit. Again, it can be hard to move around Mexico City.

The city's latest solution is one that has found success in other Latin American cities, such as Medellin, and that is: cable cars. Relative to subway or light rail, they're inexpensive. They're also good at navigating steep terrain, and their stations can be inserted into dense urban areas. This includes working-class neighborhoods who might otherwise have very limited mobility options.

For reasons like these, Mexico City has spent the last three years building three new cable car lines, the most recent of which opened just last month. The city now has the longest cable car line in the world. But more importantly, it has a new transit add-on that is moving up to 80,000 people per day.

This isn't as much as rail. But that's okay. The point of these lines is to bring more people closer in so that they can then connect to more services and other mobility options. And to do it quickly. Three new lines in three years is impressive. And from the sounds of it, it has transformed many people's lives for the better.

Here are maps of the 3 lines, zoomed out a bit so that you can see how they fit into the city's broader urban context:

One of the reasons why "new small-scale retail, service, and office uses" are now permitted in low-rise neighborhoods of Toronto -- and why many are on to talking about these uses in our laneways -- is because it's a way to serve the "needs of residents" and "reduce local automobile trips". But what are these needs exactly? And if you had to choose only one, what would it be?

Let me provide some further background.

According to this mapping, 94% of Parisians live within a 5-minute walk of a bakery. And according to this mapping, 94% of people in Mexico City live within a 5-minute walk of a taqueria. So in other words, these two cities seem to have the kind of "small-scale retail, service, and office uses" that satisfy at least some of the needs of their residents.

People in Paris need bread. And people in Mexico City need tacos. But what do people in Toronto need? I'm not sure we have a perfectly parallel thing. But according to Instacart, the top-selling grocery item last year across both the US and Canada was -- bananas. One and four carts typically contain them, and apparently this number has remained fairly consistent.

So maybe this should be our small-scale retail and walkability test metric: What % of the population lives within a 5-minute walk of fresh bananas? (I'm open to other food suggestions here.)