If you are willing to make the climb up the stairs to the top of the Guinigi Tower (and pay a fee), this is the glorious view that awaits you on a perfect blustery spring day. (Panorama - click to view larger size if your device supports that action). The tower was built in the 1300's by the wealthy Guinigi family and hosts a number of ancient and mature Holm Oak trees on the very top.
The tower stands about 125 feet high and is maybe 25 feet square at the top (just my guesstimate).
Pick a spectacular day to go up......
....you won't be disappointed.
There aren't many rooftop decks as I gaze out over the city but a few that I can see look quite inviting. Ah Lucca, lovely from any angle.