Help please. Lisbon for a day. What not to miss.

Thanks so much Harry. Merry Christmas!

Lisbon's a fun and interesting city! Our favorite things were: 1) Tram 28 to St. George Castle and then walking down to the river for lunch--great views from the castle site! 2) Listening to traditional fado music in the evening 3) Exploring the Alfama neighborhood 4) Taking a tram to Belem for the creamy egg tart pastries (Pasteis de Belem) 5) Going to the Port Wine Institute to try different varieties of port and, 6) Eating frango (roasted chicken) at a restaurant--the locals next to us shared their wine with us!

We were in Lisbon in late September of this year. My top suggestions for "don't miss it" sights/activities:
1. Take the tram up to the Castelo Sao Jorge, wander the ramparts and enjoy the views; wander down through the streets of the Alfama. Allow several hours.
2. Take the tram out to Belem for part of a day (ideally this should be a whole day but if you get an early start and move fast you could probably get to all/most of the followingin 1/2 to 3/4 of a day): visit the Monastery of Jeronimos, the monument to the discoveries, and the tower of Belem. If you have time, fight your way through the crowds to eat a pastry at the famous pastry shop there (just look for the mobs of tourists).

If all you have is two nights you won't have time for the side-trip to Sintra, which we enjoyed as much as Lisbon itself (it's an easy day trip via commuter rail from Lisbon, but you need a whole day). Unless you can re-arrange things...

Lisbon is wonderful and, I think, under-appreciated. I bet you'll like it.

Thanks so much for the help. I'm traveling alone and don't speak Portugese (I do plan on learning a few phrases),so I'm planning ahead.
I really appreciate the advice.
Sybil