Out the many miradors (lookout points) in Lisbon, which would be the best in the day the and the best at night. Do not include the Castelo of Sao Jorge as a consideration.

You'd be better off pickiong a day when there are no cruise ships in port, day or night.

The best viewpoint in Lisbon is definitely Adamastor by day and night and it is easy to reach.

My favorite miradouro in Lisbon was Miradouro Santa Luzia. It has a nice view out to the sea, but what made it my favorite was a pergola-covered walkway covered in bouganvilla. Just above Santa Luzia is Miradouro Portas do Sol, which is a bit higher and has a great view. I don't know if Miradouro da Senhora do Monte is the highest miradouro in Lisbon, but it sure felt like it. Those are the three I'd recommend for the day.