If there's one word that sums up our most popular projects of 2015, it's "diversity." The list features architects ranging from old favorites such as SANAA, Diller Scofidio + Renfro and OMA down to newer names like Sculp[IT] and Tropical Space; it also includes everything from museums to multi-family housing and spa retreats to chapels - along with the usual smattering of private residences. Interestingly, this year's list also shows the symbiosis between great architecture and great photography, with no less than 4 projects also appearing in our most bookmarked images from this year's World Photo Day. But despite their diversity, there's one thing all of these 20 projects have in common: great architecture. So settle in, relax and read on - here's our 20 most popular projects of 2015.