Located across the harbor channel from La Habana Vieja, this historic park of forts, battlements, and barracks was responsible for the protection of Havana for centuries. The complex is actually made up of two separate forts, or attractions: the Castillo del Morro and La Fortaleza de San Carlos de la Cabaña.
The Morro Castle, or "El Morro" as it is most commonly known, is the first fort you'll come to after crossing under the harbor channel tunnel. Sitting on the point overlooking Havana's narrow harbor channel, it was built between 1589 and 1630 and served as an important line of defense against pirate attacks and naval invasions. In addition to its ramparts, barracks, and banks of cannons, El Morro has a series of exhibition rooms and minimuseums. You can walk the fort's ancient streets and even climb the still-functioning, 19th-century lighthouse here. El Morro affords excellent views of Havana and the curve of the Malecón, and there are several restaurants and bars here.
About a kilometer (1/2-mile) away, and separated by a deep ravine, is the larger La Fortaleza de San Carlos de la Cabaña, more popularly referred to as simply "la Cabaña." Built between 1764 and 1774, in response to the British invasion, the long fort is a miniature city, with a high perch overlooking the harbor channel and La Habana Vieja. As at El Morro, there are several exhibition halls and a handful of restaurants, bars, and gift shops here. One of the more popular exhibition halls is the Comandancia de Che Guevara, a room where the revolutionary leader briefly set up a command post after storming the fort in January 1959. Be sure to stop in at the cigar shop, which features the longest cigar in the world, an 11m (36-ft.) stogie that hangs above your head and is duly registered in the Guinness Book of World Records.
There are separate entrance fees for each attraction. A taxi to the complex from Havana costs between CUC$5 and CUC$7. You can walk between the two forts -- it's about a 15-minute walk that's only moderately strenuous if you stick to the high ground -- or you can take a taxi between the two for under CUC$2.
The Cañonazo -- The cañonazo (cannon blast) is a picturesque ritual that takes place at La Fortaleza de San Carlos de la Cabaña every night. An honor guard in 18th-century military garb emerges from the barracks at about 8:40pm and conducts a small parade to a bank of cannons overlooking Havana's harbor channel. With pomp and circumstance, the cannon is loaded and fired precisely at 9pm. About 1,000 people show up each night, the vast majority of them Cubans. Arrive early if you want a good vantage point. The blast itself is quite loud -- you can hear it in most parts of Havana -- so protect your ears. You can combine the ceremony with a meal at one of the nearby restaurants.