Vitoria's 11th-century walls were swallowed by the expanding city over the centuries, but substantial sections survive, in some cases incorporated into newer buildings. The most visible stretch is at the back of the cathedral, where the original wall has been excavated and restored. Another good run is visible from inside the Villa Suso palace.
A self-guided "Mural" route (free leaflet at the tourist office) connects the surviving sections and explains the original defensive layout — a worthwhile way to read the old town's shape.