Havana is a city with a rich historical and architectural legacy. There are scores of sights and attractions, ranging from museums and churches to city squares and colonial forts -- and more. There's easily a week's worth of worthy attractions. I've tried to select and describe the most important sights in the listings.
At many attractions, a CUC$2 to CUC$5 fee is added on for the taking of photos, and as much as CUC$50 for shooting video. This policy seems to be applied somewhat erratically.
All of the major tour agencies offer city tours. These affairs generally take in as many attractions as can be fitted into the allotted time period. The most common tours include stops at the José Martí Memorial, a ride along the Malecón, and a walk around La Habana Vieja (including stops at a handful of churches and attractions, and, of course, La Bodeguita del Medio). Some include tours of any number of the attractions listed below, with perhaps a visit to El Morro or the Hemingway Museum thrown in, while others are theme based -- castles and forts, churches, tobacco, art, or Hemingway, for example. Different tour agencies mix and match the various attractions at their discretion. If you want to see something specific, be sure it's on the tour you sign up for. The tours can range from 4 to 8 hours in length and cost between CUC$15 and CUC$50 per person.
La Habana Vieja
In addition to the places listed, there are scores of other interesting little museums and attractions. Moreover, many of the hotels and restaurants mentioned above (including El Floridita, Hotel Santa Isabel, and Hotel Ambos Mundos, to name just a few) are practically attractions in their own right, and worth a quick visit on any walking tour.
Strolling Calle Obispo -- Calle Obispo is one of the most charming and distinctive streets in La Habana Vieja. This bustling pedestrian-only boulevard conveniently connects Parque Central and the nearby Capitolio with the Plaza de Armas and its many surrounding attractions, making it a classic route for any walking tour of La Habana Vieja.
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.