The train from the Algarve stop at two Stations in Lisbon - Entrecampos and Gare Oriente.
For Restauradores, leave the train at Entrecampos.
Take the Metro - Linha Amarela in the direction of Rato and descend at Marques de Pombal Station. Change to the Linha Azul direction Baixa Chiado and descend at Restauradores.
Note that if your intention is to catch the train to Sintra from Restauradores Station, this station is closed as the tunnel is being repaired. All trains from Lisbon to Sintra now leave from Entrecampos Station.
