Cartagena is a beautiful Spanish port town that just happens to have a rich Roman history. There are a number of well-preserved ancient sites scattered throughout the harbour area that make them easy to walk to, and this city one of the most diverse you will ever explore. 
- Museum and Roman Theatre
From the main pedestrian street, and closest to the harbour, you will find the Museum and 
Roman Theatre. This site was discovered by accident in 1987 as part of the regeneration of a humble neighbourhood. The urban landscape of the area has been incorporated into its design. The museum contains a few interesting artifacts and is your entry into the Theater. The theatre itself has been fully excavated and restored since its discovery and readily accessible to visitors. Despite a lot of steps the view from the top level is breathtaking. Part of the excavation includes an ancient cathedral which has been incorporated into the site.
- Roman Forum
Dating back to the 1st century BC this area includes public buildings, a temple and other structures. Walkways around the site allow you to view it from the above as well as an opportunity to access it at ground level. There are a number of informative placards that help put into perspective what you see.
- House of Fortune
Located well underground, this residence dates again from the 1st century BC. You enter the home from the rear landing and follow through to what would have been street level. There is another area underneath the home that predates it and is presumed to have been a shop. This would have been the home of a wealthy merchant because of its size and opulence. Most fascinating is the still colourful frescos that once decorated the dining area.
- Augusteum
Again well underground this excavation unearthed the remains of two public buildings. They may have been used for religious purposes and as a meeting place devoted to the worship of well known emperors.
- The National Museum of Underwater Archaeology
This museum includes many centuries of archaeological finds, dating back of course to the Roman habitation of Hispania. There are the remains of a vessel from the Phoenician era as well as sets of items found in Roman shipwrecks.
You can check the Cartagena Tourism website for the cost and hours for each of these sites, but I can tell you they are all very reasonable. Put together they provide a fascinating overview of the ancient history of this area. Because they are all very close together you can see everything and still have time for wine and tapas.