This summer, about 17 million people stayed at Airbnb properties (including yurts, boats and castles)

Airbnb has published its 2015 summer travel report, and the summer sun was sure shining brightly for the vacation rental company — about 17 million people stayed at Airbnb properties this summer.

I, for one, have no idea how to visualize that massive number, but Airbnb put the stats in context for us: 17 million is more people than the individual population of Greece, Sweden or Switzerland. It's also more than the number of tourists Paris, Dubai, or New York welcome in a year.

Airbnb guests stayed in 191 countries and 34,000 cities around the world.

The blockbuster night for Airbnb this summer — and its biggest ever — was August 8. Almost 1 million people were staying at Airbnb properties in 150 countries around the world that night. As Airbnb put it in a report:

If the Airbnb community was a city, on August 8 it would have been the 10th largest city in the United States.

Three of the most popular travel routes were Paris to Lisbon, New York City to the Catskills and Hudson Valley; and Seoul to Osaka. Curious about the Airbnb guests themselves? The average age was 35 years old, with women accounting for 54% of guests and men 46%.

And some of these people were really after an alternative stay.