Tarraco, now called Tarragona, was an important Roman provincial capital and was the first Roman settlement on the Iberian peninsular, according to the UN. The town is on a steep site and the Roman layout, with a religious area (now under the Gothic cathedral) at the highest point, a forum slightly lower down and the circus and amphitheatre below that was apparently and influential one.
The remains are mostly under the medieval city although there is a substantial stretch of wall. Otherwise, the bits that one can see are mostly fragments sticking up into a square or excavated in a cleared area.
There are other remains out of town but I wasn’t able to get to them. The largest visible monument in town, other than the walls, was the amphitheatre:
Which I’ve attempted to render in Lego, at least in part:
Let us hope that tomorrow’s monastery give me more to work with, model-wise!