LISBON, Portugal - Detail of the Arco da Rua Augusta on Pra&ccedil;a do Com&eacute;rcio. Known as Commerce Square in English, Pra&ccedil;a do Com&eacute;rcio is an historic square in the Pombaline Downtown district of Lisbon, next to the Tagus River. The Arch was built to commemorate the rebuilding of the city after the 1755 earthquake.