Final answer:
Georgetown, the capital of Guyana, is located at the mouth of the Demerara River. It's an important economic and cultural center with notable British colonial architecture.
Step-by-step explanation:
The city located at the mouth of the Demerara River is Georgetown. Georgetown serves as the capital of Guyana and is the country's largest city. It's an important port and a cultural and economic center, significantly influenced by its location on the Atlantic Ocean at the river's delta.
The Demerara River is integral to the economic life of the city, as it allows for the shipping of sugar, one of Guyana's primary exports. Georgetown is known for its British colonial architecture, including St. George's Cathedral, one of the tallest wooden church structures in the world.