After reading many travel reviews on Cartagena suggesting that less time is better (cost, crowds and hassle were frequently mentioned) we only gave ourselves one full day to see the old town. The highlights can certainly be seen in a busy day but I felt rushed and didn't do all that I'd hoped.

As a strategic Caribbean port for the colonial Spaniards, Cartagena was wealthy and needed protection. A lot of protection. Inscribed as the largest system of military fortifications in South America there are a lot of forts surrounding the bay/port and the wall surrounding the colonial core is still intact and good for strolling as well. We started with a visit to the massive Castillo de San Felipe, the largest and most important of the forts before venturing into the colonial core.  Within, the centre is well preserved and densely packed with narrow streets and more traffic than it needs to have. Maybe it is obvious because of its location but the overall feel is much more Caribbean than South American. Think Havana, not Lima. 

We were lucky and didn't have any cruise ships unloading hoards of tourists to overwhelm the centre but it still felt busy and there is no doubt this is the most visited city in Colombia. Trips into the bay or out to nearby islands should give a better perspective of the overall defensive strategy but we didn't have time. I was happy to have gotten a window seat on our flight out with an excellent birds-eye view of the bay to better appreciate how complicated its defense would be.