This restaurant/bar at the top of the Sheraton Hotel offers an excellent view of the city by night and the cocktails are fairly inexpensive (in comparison to other European capital cities).
Rua Latino Coelho, 1;
tel: 21 312 0000;
www.sheratonlisboa.com/eng/restaurante/bar_panorama/
www.starwoodhotels.com/sheraton/property/overview/announcements.html?propertyID=292