Final answer:
The capital and largest city of Saint Lucia is Castries, featuring Morne Fortune and prominent sites like Derek Walcott Square and the Cathedral Basilica of the Immaculate Conception.
Step-by-step explanation:
The capital city and the largest port city of Saint Lucia is Castries. Castries is a vibrant city which is not only the seat of government but also the center of tourism and commerce in Saint Lucia. The city is overlooked by Morne Fortune, an important historical site, and features Derek Walcott Square and the Cathedral Basilica of the Immaculate Conception, indicating the city's cultural richness.
Castries has major significance given that it is an important port for cruise ships in the Caribbean, particularly crucial for the local economy and tourism which is a lifeline for the islands of the Lesser Antilles, such as Saint Lucia.