Le Chat has an awesome view, it's just perfect to finish the day or to have a long lunch. You can enjoy the view over the 25th April Bridge and the Tagus River to the other shore and maybe you will see a cruise ship leaving Lisbon and heading towards the ocean.
This glass cube is very close to the National Museum of Ancient Art. It has seats inside, and outside on the terrace. Even in winter the terrace is appealing, with heat lamps and blankets provided.
Regarding the menu, I would suggest sharing some appetizers like sweet potato chips, sautéed shrimp, and a traditional Portuguese dish, Peixinhos da Horta. There are plenty of options for your main course. Try another typical Portuguese ingredient, caco bread, which is used for burgers and sandwiches.