Lisbon is a beautiful city, with gorgeous miradouros (viewpoints), cheap beer and old world trams and neighbourhoods such as Alfama. Prices are very reasonable also. You will fall in love with this beautiful city and its friendly inhabitants!
Insider Tip:Visit Sintra, a mere 40 minute tram ride away from Rossio train station. Go get a Ginginha (cherry shot) from one of the tiny bars around Rossio train station- starts any night off in style! Go to the Bairro Alto on a Friday/Saturday night for pure chaos and an amazing atmosphere!