When you enter Seoul from the airport by bus, you see a couple of flat-topped hills across the river next to the World Cup soccer stadium. They're about 100 met

When you enter Seoul from the airport by bus, you see a couple of flat-topped hills across the river next to the World Cup soccer stadium. They're about 100 meters tall and just over 2 kilometers from end to end. You wouldn't find anything unusual about them if you weren't used to the Korean landscape -- there are no naturally flat-topped hills around here -- but that's the old garbage dump for this city with a population of 10 million. They surrounded the garbage with concrete walls to prevent wastewater from leaking into the river, poured a thick layer of soil on top of it, planted trees, and built walkways. Now it's a public park. The underlying garbage still emits methane, which is collected and burned to power the adjacent soccer stadium and other facilities. We humans made these mountains of crap ourselves. We might not have the budget and/or political will to remove them, but we do have the capacity to make them look significantly less crappy, and perhaps even useful, if we want to.