Manaus is located in the middle of the Amazon rainforest, and access to the city is primarily through boat or airplane. This isolation helped preserve both the nature as well as the culture of the city. The culture of Manaus, more than in any other urban area of Brazil, preserves the habits of Native Brazilian tribes. The city is the main entrance to visit the fauna and flora of the Brazilian Amazon. Few places in the world afford such a variety of plants, birds, insects, and fishes. It was known at the beginning of the century, as "Heart of the Amazon" and "City of the Forest".Currently its main economic engine is the Industrial Pool of Manaus, the famous Free Economic Zone. The city has a free port and an international airport. Its manufactures include electronics, chemical products, and soap; there are distilling and ship construction industries. Manaus also exports Brazil nuts, rubber, jute and rosewood oil. It has a cathedral, opera house, zoological and botanical gardens, an ecopark and regional and native peoples museums.