We recently (9-3-18) did the:
CARTAGENA & LA MANGA 4 1/2 HOURS At Cabo de Palos, a gray stone lighthouse that began operating in 1865, you'll stop for photos. Driving on to La Manga Cavana, you'll have approximately 45-minutes of free time for shopping or a snack before heading back to Cartagena. After riding an elevator up to Conception Castle, you'll enjoy a superb panoramic view of Cartagena, its naturally sheltered port, and even an old bullring built over a Roman gladiator arena. You'll have plenty of time to wander about and drink in the views, before descending to elegant Calle Mayor, one of the city's finest thoroughfares for shopping and dining.
Guide was mediocre at best. Many people abandoned the tour when it got close to the pier. Description makes it sound much better than it actually was. I enjoyed the tour sites, and although I would agree with others who abandoned tour based upon guides performance I stuck it out to the end. I do my own research and in this case was as knowledgeable as the guide was able to express her knowledge. She may have known more but was very limited in her ability to get the info across to those on the tour.