Praça do Comércio is a symmetrical U of yellow arcaded ministries opening directly onto the Tagus, with a bronze José I on horseback in the middle and a triumphal arch on the north side. The square is meant to be entered from under the arcades, so that the open space and the river arrive together. It is wide enough to feel like part of the estuary, with the old quay steps running down into the water.
The royal palace stood on this ground until the morning of 1 November 1755, when an earthquake struck, a wave came up the Tagus, and fires burned for days. The Marquis of Pombal cleared the ruins and rebuilt the quarter to a single plan, and this square is its river frontage. He built it to show that a whole city could be planned on paper first. Climb the arch at the north end and Rua Augusta runs straight away to the Rossio with the castle hill off to the right, which shows what Pombal did better than any plaque.