Gunpowder was made at Barcarena for more than four centuries. The royal powder factory in the valley of the Ribeira de Barcarena, a small stream that winds down to the Tagus estuary, supplied the Portuguese army and navy from the sixteenth century until the twentieth, and the old mills, workshops and storehouses have been restored as a cultural park, with a museum and gardens by the stream.
Barcarena lies in the municipality of Oeiras, in the hills west of Lisbon, between the city and Sintra. Oeiras was the home of the Marquis of Pombal, the powerful minister who rebuilt Lisbon after the great earthquake of 1755, and his palace and gardens are open to visitors.
The Marginal, the coast road from Lisbon to Cascais, runs a few kilometres south, along the estuary and the Atlantic coast, with beaches, forts and promenades. It is a scenic ride, though often busy, and the beaches at Carcavelos and Paço de Arcos are popular with surfers and swimmers.
Coming back from the Douro valley, a long weekend of vineyards and river views in the north, you finish on the A1 motorway south and the ring roads around Lisbon. Traffic can be heavy, especially on Sunday evenings. Several Portuguese motorways use electronic-only tolls, so check how a foreign-registered bike pays before you go.
Any neighbourhood pastelaria will do for the last ritual: a bica, the short Lisbon espresso, and a pastel de nata still warm, with cinnamon shaken over the top. Fuel is on the main roads into Oeiras and Queluz.