Where is cycling sport most popular?

Could you please enlighten me on the whereabouts where cycling sport holds the most sway? I'm genuinely curious to know which regions or countries embrace this exhilarating sport with the utmost fervor and dedication. Is it perhaps in the hilly landscapes of Europe, where cyclists push themselves to the limit on grueling climbs? Or does the popularity stem from the bustling metropolises of Asia, where cycling events attract massive crowds and inspire the masses? I'm eager to learn about the cultural and geographical factors that contribute to the prevalence of cycling sport in its most beloved havens.