We are visiting Lisbon in October and are considering an apartment that is within our budget and has great space. But it is near the Colombo Shopping Center and we are wondering if that is too far outside the areas we will be touring? We walk a lot but I see that we will have to take the metro in to the city everyday to begin our walking tours. Is the metro fairly easy to navigate and is it cost effective? This apartment is priced great but if we have to pay for transportation every day, we are not sure if it is worth it. Thanks for you help!