Start and finish here and you are on the south bank of the Tagus, in the pine-scented suburbs of Almada between Charneca de Caparica, Corroios and Sobreda. It is a residential area of houses, schools and supermarkets, without much to look at in itself, but its position is very good: close to Lisbon across the river, and close to the open roads that lead south to the Arrábida hills and the city of Setúbal.
From here the Arrábida and Setúbal ride heads down the Setúbal Peninsula, and the contrast with the suburbs is quick and sharp. Within half an hour you can be on the coastal road in the Serra da Arrábida, a limestone ridge that rises straight from the sea, covered in dense Mediterranean scrub of myrtle, rosemary, wild olive and strawberry trees. The views from the ridge road down to coves of turquoise water are among the best in the Lisbon region, and the bends are proper, tight and steep in places. The road through the natural park has strict rules in summer, with access to some beaches limited, so check before you count on a swim.
Setúbal itself is a working port town with a busy fish market and a famous local speciality, choco frito, fried cuttlefish served in strips. Down the coast, Cabo Espichel is a lonely headland with a pilgrimage church, cliffs dropping hundreds of metres into the Atlantic, and dinosaur footprints preserved in the rock. Wine villages such as Azeitão, between the hills, are known for Moscatel de Setúbal, a sweet fortified wine, and for a small, runny sheep's cheese.
Back at the start, the roads are suburban: roundabouts, traffic lights, buses and patches of cobbles. Rush hour can be heavy, especially toward the bridges into Lisbon. The A2 motorway and the N10 run east of here, but for the Arrábida loop the smaller roads through Sesimbra or Palmela are more fun once you clear the housing. Expect wind near the coast and some sand on the tarmac.
Fuel, food and coffee are easy to find nearby; the suburbs have stations, supermarkets and the usual Portuguese pastelarias. If you finish in the late afternoon, take a short ride west to the edge of the Caparica cliffs and watch the sun set into the sea, then reward yourself with grilled fish in Costa da Caparica, a few kilometres away.