One of the most diverse and populated countries in Southeast Asia, Indonesia is comprised of more than 15,000 islands covering an expanse of nearly 2 million square kilometers, including Java, Bali, Lombok, and Sumatra. Bali is well known to travelers around the world for its diverse landscapes from beaches to volcanic mountains, exotic Hindu arts and culture, and luxury villas and resorts offering a world-class holiday. Neighboring islands of Lombok, the Gilis, and Flores are home to some of the region’s best diving and snorkeling, known for their coral reefs and diverse sea life. The spiritual and cultural heartland of Java, Yogyakarta has enjoyed a harmonious mix of Buddhism and Hinduism since the 13th century, resulting in two of the greatest religious monuments still standing: the Borobudur and the Prambanan Temples. Rich in biodiversity and teeming with flora and fauna, Sumatra beckons adventure and nature enthusiasts with trekking opportunities to see orangutans and volcanoes and to explore different ethnic cultures. Indonesia has over 600 airports. Two of the busiest are the Soekarno–Hatta International Airport in Jakarta and Ngurah Rai International Airport in Denpasar (Bali).