How to see Lisbon in a day?
Ok this is not a comprehensive guide but I believe it will suffice: Take the Sightseeing tours offered by the Carristur which is also the bus and tram netzork of the city. It offers a 14 euro yellow and blue line tour which are value for money. I took the yellow line since the blue one is overbooked.
The hop on hop off bus tour comes with headphones and commentary. The additional benefit of using this tour is that you can continue to use the same ticket without the need to validate on later trips for all buses and trams during the same day.
With this tour i managed to see the highlights of lisbon which includes the older and modern part including a short description of the citys history.
Another must go is the castle which can be visited by bus 37 at rossio metro. Entrance is 3 euros but worth the price as you get a panaromic view of the city...
The jeronimos monastery is another highlight which should be visited.
I also love to trawl the narrow streets of protugal which looks like a ripped off set of old italian movies. very lovely.