There are so many things to remember in order to be best prepared for a trip–especially in our technology driven world. Downloading the map(s) of where I am going from http://www.maps.me allows me to navigate even when I don’t have wifi or cell service. As an example, we were able to easily circumnavigate the streets of Venice–not a trivial feat. I also download any public transportation maps including approximate time schedules. One caveat–do verify the actual time schedule on the day you plan to use it.
I also download city guides (if available) from TripAdvisor before I leave home. That way, if I am out and about and want to check reviews, I have a reference guide. Before I discovered the offline use of TripAdvisor I was constantly in search of places with wifi to be able to look something up. In TripAdvisor, I enter the city I am looking for, in this case, Lisbon. I scroll down until I see “Get to know Lisbon” and then download. After downloading, I go to “Downloaded Cities” (find it in the pull-down menu under “me” on the mobile app). Once downloaded I am able to access all of the same TripAdvisor info without the need for wifi.
Rick Steves has great audio tours of Europe. The app is available for free. I download the tours before I leave home. There are walking tours–the one of Lisbon was a great intro. There are also audio tours about the culture or food–for example, Fado music in Lisbon. I frequently will listen to these audios on the plane there to stoke the excitement.