When Newfoundland and Labrador's St John's became a European harbour back in the 1500s, it looked a lot different than it does today. Europeans were drawn to Newfoundland in search of cod which, at that time at least, swam in the seas in great numbers, and St John's became a major fishing port. By the early 1600s, a permanent English settlement around the harbour and slowly developed into a commercial centre. Battles between the English and French (and less frequently the Spanish and Dutch) and increasing pirate activity saw the town fortified - including the creation of several forts. Despite the constant conflict, St John's continued to grow. Today, St John's is the capital of Newfoundland and Labrador, and it's harbour filled with large industry vessels, cargo ships, cruise ships, and small tourist boats that take eager visitors around the coast.
What has not changed so much is the shape of the coast. It is this shape that made the area the perfect harbour. A harbour needs to provide a safe place for boats to go and even stay for a long time. With high cliffs surrounding the harbour, boats that enter find some protection from strong winds that ravish the region, and the waters much calmer than found in the open ocean or even on the other side of the cliffs.
The harbour would not be so effective if it had a wide opening though. "The Narrows" is the only entrance and exit to the harbour. It's 91 meters long, and at its narrowest point, it reaches just 61 meters. Its depth reaches just 11.8 meters at low tide. Although "The Narrows" provides protection from the elements, in times of war it could also act as a trap which could prevent boats escaping an enemy attack or heading out to fight leaving the harbour unharmed. It could also act as a strong defence. The one entrance to the harbour - and the only point of entry to the city from the sea was heavily defended by forts from the mid-1600's, but it didn't stop there. In the 1800's a chain was laid across the seabed at the narrowest point. When an enemy ship tried to enter the harbour, the hidden chain could be raised and the enemy ship…well it didn't do too well. More recently in World War II, the threat of submarines sneaking into the harbour was real. Again this narrow point became an ideal defensive position, but this time it became home to a steel mesh rather than a chain.
No harbour is perfect though. In 2017 high winds reaching 95 kilometres per hour blew a shipping container into the water where it had to be rescued by a brave tugboat crew, and icebergs do manage to make their way through the narrows where they are a nuisance to seafarers, and a wonderful photo opportunity to sightseers.