What historical city within Manila was designed as a fortified city?

Intramuros is historically significant as it was designed as a fortified city within Manila. Established during the Spanish colonial period in the late 16th century, Intramuros was meant to protect the city from foreign invasions and attacks. The walls surrounding Intramuros were constructed using solid stone and were equipped with various fortifications and bastions, showcasing military architecture of that era.

Intramuros served not only as a defensive structure but also as the seat of political, religious, and economic activities during Spanish rule. Its intricate layout included streets, plazas, and buildings that reflect the Spanish colonial heritage, making it a pivotal point in Manila's history.

The other options, such as Metropolis, Megalopolis, and Chicago, do not pertain to the historical context of Manila as a fortified city. Metropolis and Megalopolis are general terms used to describe large urban areas, while Chicago is a well-known city in the United States that does not fit the description of a fortified city in Manila. Thus, Intramuros stands out uniquely as the correct answer.