If you like to do some shopping while you are in another city, here's some places you could visit
Visit the streets of the city center were you can find a lot of stores
Vasco da Gama Shopping
If you go to Parque das Nações you will find this shopping alongside the oceanary, a telepheric and Altice Arena.
Next to Estádio da Luz in Benfica you can find this big shopping
Freeport Lisboa Fashion Outlet
If what you love is some serious sales in you favorite brands than this is the place for you. You just need to cross the bridge, drive to Alcochete and you will find this amazing outdoor outlet.