Rua das Douradores is only about 2 mins walk from the riverside Praça do Comércio square which is excellent for photographs of the grand buildings. Not much else here although handy tram routes pass through. There is an area of restaurants in renovated warehouses by the river (Doca do Jardim do Tabaco) and the Lux club (said to be the best club in Lisbon, but I didn't go) but this is further up by Santa Apolonia station - a bit far to walk.
Looking again at Google maps, from Rua do Duque there is the Calçada do Carmo down to Rossio Square which is probably the quickest way down to Baixa (streetview shows the pavement is steps at first, then a slope lower down). I recall now I did see this way zigzagging up beside Rossio station, but never used this route.
As Rua do Duque is up by the Igreja de São Roque (probably the most spectacular chuch in Lisbon) you are pretty much in Bairro Alto anyway (immediately west of this church) so you'd only be a couple of mins walk. You'll also be very near the Cervejaria Trindade which is worth a look even if not drinking/eating
I wouldn't say one is more strictly central than the other, but Baixa tends to be referred to as the centre as it's the flat bit between the two main hills. It's not the distances so much as the hills will be the issue if you're walking.
Edited: 12 February 2012, 8:44
