28 Hours in Lisbon

With that very short amount of time I would stay very central (right near Rossio square) and plan a walk up through the Alfama to the Castle. There are walking tours (which you can modify to include what you want) in most major guidebooks. If you have time Sao Vicente de Fora has some great views and amazing tile work. Here's my photos of Lisbon - https://andiamo.zenfolio.com/p980488540

You can also venture to Sintra for part of the day to explore the castles there. Sintra is 1 hour from Lisbon by train.

http://www.sintra-portugal.com/guides/Lisbon-to-Sintra.html

http://www.sintra-portugal.com/index.html

I take it you are suggesting taking the time to go to Sintra over exploring Lisbon itself? I assume it would take a most of the day to travel and explore there. It looks very cool!

I would stay in Lisbon with such a short time vs. wasting precious hours getting to and from Sintra.

Take a walking tour that will give you an overview of the neighborhoods (very hilly) and get you to some of the prominent viewpoints.

Many visitors go out to Belem - you could do that.

I agree with Isabel. With so little time, I would visit the Sao Jorge Castle, which has gorgeous views of the city. We enjoyed the castle; you are outdoors all the time, and the peacocks are fun. Then wander through the Alfama. We followed Rick Steves walking tour through the Alfama. it brought us into the heart of the Alfama, far from the tourist crowds. This is where people live. We saw clothes drying outdoors, heard radios or tv's through open windows, etc. An elderly woman set up a small table under a tree and sold those cherry drinks. Forgot the name. You can also follow Rick's other walking tours, which will bring you to miradouros (viewpoints). Personally, I would do this instead of visiting Belem, which is lovely and we loved the Jeronimos Monastery in Belem, but our day spent at the castle and exploring the Alfama was our favorite. We also visited the small Mosteiro De Sao Vicente De Fora, with its gorgeous tiles and spectacular views from its rooftop. All done in one day.

I like the walking tour idea. Is there one part of the city that we should stay to make the best use of our time for the wandering?

Thanks for all your thoughts

I loved Sintra, but agree that with such a short time in Lisbon, taking the time to travel to and from Sintra would not be worthwhile. It’s not just the 1-hour transit time, but the added time getting to and from the stations at each end, waiting for the trains, etc. Then the sites in Sintra are quite spread out.
A good guided walking tour would be a great use of 3-4 hours in Lisbon. I took a great tour called something like “Food and Culture Tour”, wish I could remember the name of the company, but the guide was terrific, informal, enthusiastic, very well informed. He said the philosophy of the company and tour was to take people “off the beaten tourist track” through old neighborhoods and mom-and-pop food places. The tour started at Rossio Square, then went through into the Alfama and Mouraria neighborhoods, with both cultural and food and beverage stops, then down to the ferry port and we took the ferry to the other side of the river, for extensive tastings at a seafood restaurant over there. The tour ended at the return ferry. My kind of experience! I would love to take that tour again!!
Another experience unique to Lisbon is the Museu do Azulejo (Tile Museum), which includes wonderful exhibits of the tile work, ancient up to modern, so common in Lisbon and around Portugal. I simply love the tile work! Nice garden bistro for lunch there too. Quick and easy to get to by taxi, but somewhat time-consuming by public transit as it is about a 15-minute walk, not very interesting, between the nearest station and the museum.
Also unique would be a good evening fado bar, best if you can get a good recommendation for a real locals place, probably for late evening. There are fado tours too, often with dinner, but I suspect they mostly go to spots geared to tourists. Not so bad, but likely less than authentic. I was somewhat disappointed by the Fado Museum in the Alfama, although there was a wall with big photos of some of the most famous fado singers, with headsets so you could listen to the varied styles of fado music of each one. Worthwhile if music is really your thing.
There are various sites in the Belem area, but a visit there, including transit back and forth, would take most of your day, to the exclusion of other visits.
Lisbon is a wonderful city, with great neighborhoods but without obvious “world class” sites. So you really should do some research and fill your limited time with things that are uniquely Portuguese and match your personal interests. Enjoy!

Great ideas! Thanks for all the information. I think we will be doing a lot of walking!