Ireland is sometimes referred to as the "Emerald Isle" due to its lush greenery. The May birthstone is emerald. Seattle is sometimes referred to as the "Emerald City", because its abundant rainfall creates lush vegetation. In the Middle Ages, "The Emerald Tablet of Hermes Trismegistus" was believed to contain the secrets of alchemy. "Emerald City", from the story of "The Wonderful Wizard of Oz", by L. Frank Baum, is a city where everything from food to people are emerald green. However, it is revealed at the end of the story that everything in the city is normal colored, but the glasses everyone wears are emerald tinted. The Green Zone in Baghdad is sometimes ironically and cynically referred to as the "Emerald City". The "Emerald Buddha" is a figurine of the sitting Buddha, made of green jade (rather than emerald), clothed in gold, and about 45 cm tall. It is kept in the "Chapel of the Emerald Buddha" (Wat Phra Kaew) on the grounds of the Grand Palace in Bangkok. The Emerald Triangle refers to the three counties of Mendocino, Humboldt, and Trinity in Northern California, United States because these three counties are the biggest marijuana producing counties in California and also the US. A county-commissioned study reports pot accounts for up to two-thirds of the economy of Mendocino. "Emerald Cities: Urban Sustainability and Economic Development" is a book published in 2010 by Joan Fitzgerald, director of the law, policy and society program at Northeastern University, about ecologically sustainable city planning.