That is true. Oslo unlike Amsterdam is not at all flat, with many having 100-200m of height to climb on their way home if going downtown for work or shopping.

However, electric bikes are changing that equation drastically. With an e-bike those climbs are not an issue at all. So there's been a good uptick in people who ride bikes here.

Of course, e-bikes are quite expensive compared to regular bikes, but compared to owning a car they're quite cheap. So for someone living in Oslo, having an e-bike and renting a car a few times for the long trips can be a very good deal.

There are other countries with cycling cultures that aren’t flat.

Sweden is very not flat, and they have plenty of extremely well used cycle infrastructure. Hell their kids cycle to school in snow.

It's debatable, though, whether riding a bike in the snow is really such a great idea.

https://www.tandfonline.com/doi/full/10.1080/15389588.2019.1...