While Dubai’s been busy assembling its fantastical cityscape, Abu Dhabi may have trumped its emirate neighbor in one fell swoop. The UAE capital — the world’s third-largest oil producer — is spending $5 billion to create the planet’s first carbon-free city. The ubiquitous Norman Foster has been recruited to design Masdar, a walled city-within-a-city slated to open in 2009. What it will have (a photovoltaic power plant, an institute of science and technology, 100,000 residents) is not nearly as thrilling as what it won’t have (cars, waste, taxes). Inside this self-sustaining utopia, people will travel by an eco-friendly transit system; energy will be harnessed by sun and wind farms; and all taxes will be abolished. That last enticement alone should turn even the most gluttonous gas-guzzlers into believers. And as travelers, we can also have a guilt-free, carbon-free vacation in the Arabian sun — so long as we choose Masdar instead of the $3-billion Emirates Palace hotel, and if easyJet (currently touting their future C02-reduced jets) start flying there.