Port Jackson in Sydney, Australia, is the deepest natural harbor in the world. The harbor has a perimeter of around 200 miles, and in some places it's 100 feet deep. It is also home to 550 species of fish, making it one of the most diverse harbors in the world.
Port Jackson is better known as Sydney Harbor in many places outside of Australia. It's the site of the Sydney Opera House and the Sydney Harbor Bridge. The harbor is also the site of the first European settlements in Australia. Governor Arthur Phillip established the colony that would later become Sydney on the south side of the harbor in 1888.