For me, Tarraco (Tarragona as it is called today) is a light 3.5 stars for me, bordering on a 3. As you can gather from the other reviews on here, none of the individual locations are particularly jaw-dropping for this WHS, but taken together they make up quite an interesting vision of Roman life. Also, the fact that this is one of the first Roman settlements not only in Spain, but outside of Italy as a whole is just plain cool.

Tarragona has done a decent job of making each of these locations accessible and providing explanations of what you're seeing via signage and audiovisual displays at each of them. If you want to just hit the biggest highlights and avoid the stuff that are mostly just "rocks" or a piece of hardly-identifiable architecture, then I recommend doing the Amphitheatre, the Circus, the Walls, and the Aqueduct. This is more or less what my group did, as we were limited on time and there is only so much I can convince my non-WHS friends to go out of their way for. Of all these items I'd say the Aqueduct was the most impressive but the Circus really surprises with its unassuming entrance and then vast network of ruins to see once you're inside.

Be aware that most (not all) of these locations you will have to pay separate entrance fees for, so it can get slightly spendy if you're trying to hit all of them. Also it's important to know that a lot of these locations are all centrally located together in the downtown area near a whole bunch of other fascinating non-WHS stuff to do. (Cathedrals, museums, etc.) If you want to really take full advantage of all the historic richness that Tarragona has to offer, you could easily fill out 1–2 entire days seeing everything. Even if you're more limited time, though, Tarraco is worth a visit.