Madeira, Portugal

Madeira outpaces #10 Zanzibar as a year-round garden retreat, with its volcanic origins creating a microclimate that sustains over 1,500 species of plants. The island's 2,000 kilometers of levada walks—irrigation channels built since the 16th century—offer the most accessible laurel forest exploration in the world, a UNESCO heritage site. Visitors can hike to cliff-edge vineyards at 400 meters altitude, where the fortified wine withstands Atlantic gales and once accompanied Napoleon into exile. This oceanic garden also supports over 80% of the world's bananas labeled as 'Madeira' under EU protection. Compared to the typical average island of 100 square kilometers, Madeira spans 800 and delivers a density of biodiversity that is 30% higher than the runner-up in this list, all within a comfortable 20°C year-round climate.