The vast Fortaleza de San Carlos de la Cabaña, known as ‘La Cabaña’, running beside the harbor, was constructed after the English capture of Havana in 1763. The largest of the military structures built by Spain in the Americas, this fortress was completed in 1774 and its presence formed an effective complete deterrent against the country's enemies. The polygon, occupying an area of around 10 hectares, consists of bastions, ravelins, moats, covered walkways, barracks, squares and stores.  It is impressively well preserved, and the gardens and ramparts are romantically lit in the evening. This fortress hosts the spectacular nightly ceremony of El Cañonazo de las Nueve (cannon fire at 9), the firing of a cannon that marked the closing of the city gates, one of Havana's longest-held and most attractive traditions.

The Templete, a small neo-classical style construction, was built in the second half of the 18th Century. It is located in Plaza de Armas. This was the site where the first public mass was celebrated and also the site of the first town council of the nascent town of San Cristóbal de La Habana. The Templete resembles a Doric temple and houses three commemorative canvasses by the famous French painter Juan Bautista Vermey. One of the walls exhibits the plate that declares Old Havana a World Heritage Site.

This square dates back to the first half of the 17th century. Its location, just a few metres from the bay, led to it becoming an important trading square over the years. It is said that around the year 1600 the first fountain of the city could be seen at this square. In 1836 it was replaced by a beautiful fountain made of white Carrara marble by Giuseppe Gaggini, under the good auspices of the Villanueva Count. This fountain is called Fuente de los Leones (Lions Fountain). On its paved area stand two noteworthy buildings: the Monastery and Basilica of San Francisco de Asís, which today houses the Museum of Religious Art and a concert hall. It is also where the Lonja del Comercio (Chamber of Commerce) is located, inspired by Spanish Renaissance architecture and topped by a dome on which a sculpture of the god Mercury stands. Among the houses built around the plaza, the house of the Arostegui family, residence of the Captain Generals until the completion of the City Hall at the end of the 18th century, was erected.

The neighbors of the town insisted to the town council on the need to create a new public square for their amusement. In 1587, the town council decided to use as a public square the area behind the Convento de San Francisco, which was being built at the time. During the latter decades of the 16th century, this square was called the Plaza Nueva (new square), but from the 18th century onwards, once the Plaza del Cristo had been built, it began to become known as the Plaza Vieja (old square). The most remarkable feature of this square are the buildings around it, with their unquestionable historical and artistic importance of having been the blueprint for a style of architecture which, along with certain developments, subsequently spread throughout the city and characterised the Cuban architecture of the 18th century.