Quinta do Seixo, owned by the port house Sandeman, sits on a high spur above the south bank of the river between Pinhão and Tua. It is one of the most professionally run visitor quintas in the valley: regular guided tours in several languages, a modern winery with stainless lagares alongside the traditional granite ones, and a hillside terrace where you can sit with a glass of tawny and look across to the terraces opposite.
For first-time visitors it works well — you don't need a reservation in the off-season — and it gives you a fair sense of what a working modern port estate looks like. The view alone justifies the drive.