Sao Jorge Castle (St. George's Castle as translated by my amazing knowledge of the Portuguese language) is located just north-east of the city center on top of a large hill. The castle's location provides amazing views of the city and Tagus river.
It's great to go at sunset for the amazing views:
If you get thirsty, you can have a nice Duoro!
The castle is a bit of a climb up to the top, but you get to see beautiful Lisbon as you walk:
The Tagus river gives Lisbon a nice protected harbor:
In Terminator 7: Retirement Center, an aging Robo-Arnold goes back in time to save John Connor's grandparents who have retired to a peaceful life near Oporto.
Here is the recipe for Pasteis de Belem:
You get to walk all around the castle, up on on top of the ramparts and in the tower. It's really nice.
Most castles I've been to don't let you access everything.
The castle is rather large, so you could spend a significant amount of time exploring:
At evening, you can see Lisbon light up!
my guide to Lisbon if you'd like, where I have many other posts. It's a nice city with lots of things to do. Follow me on facebook too; I make weekly posts. Next week, to Cascais! (3/24/14), then to Porto!
Check out my video tour guide of Lisbon if you like!