As of 2026, the world's largest national botanical gardens serve not only as sanctuaries for biodiversity but also as arenas where geography meets climate. Ranking first, the Kirstenbosch National Botanical Garden spans an impressive 528 hectares. As the world's first botanical garden dedicated to indigenous flora, it sits at the heart of the Cape Floristic Region, home to over 7,000 native species. Interestingly, its scale often dwarfs the gardens at the bottom of this list by several times. Furthermore, by leveraging the vertical climate zones of Table Mountain’s eastern slopes, Kirstenbosch achieves a density of ecological diversity that far exceeds flat-land botanical gardens, effectively condensing the entire evolutionary history of South African flora into a single, majestic landscape.