30 Jan Old Havana
You simply can’t travel to Havana without checking out Old Havana (Habana Vieja.) Many tourists choose to take the tourist jump-on-jump-off bus to cover the touristic sites. If you only have half-a-day to see Havana this is good enough to cover a lot in a short period of time.
If you have more time you should spend at least one day exploring Old Havana and see the real deal with walking along the backstreets and see all the colourful houses along the way. Here is my recommended self-guided walking route of Old Havana.