Previously called Lansdowne Road Stadium, the recently renovated Aviva Stadium is the oldest international stadium in the world. In designing the 50,000-seat sports park Populous and Scott Tallon Walker Architects sought to minimize the structure’s environmental footprint as much as possible. The sweeping roof of the stadium does double duty in terms of green features – it’s constructed from sturdy transparent materials that shelter the interior while allowing daylight to seep in, and it harvests rainwater to irrigate the sports field. The north end of the stadium features a smooth slope that dips to allow daylight to reach nearby residences, and a smart set of efficient fixtures conserve energy — for instance, the escalators only operate when people are standing on them.