Indonesia is the world's largest archipelagic state, consisting of over 17,000 islands. It spans across Southeast Asia and Oceania, making it a transcontinental nation. Jakarta, the current capital, is located on the island of Java, which is the most populous island in the world. The country is situated on the Pacific Ring of Fire, giving it the highest number of active volcanoes in the world. Its five main islands are Sumatra, Java, Borneo (shared with Malaysia and Brunei), Sulawesi, and New Guinea (shared with Papua New Guinea). Indonesia's geography includes vast tropical rainforests, second only to Brazil in size. The 'Wallace Line' is a faunal boundary line that passes through Indonesia, separating the ecozones of Asia and Wallacea.