The Alhambra Palace is definitely the top attraction in Granada city. It is the most visited monument in Spain and it is both a palace and a fortress. Tickets should be purchased in advance since they sold out quite quickly. For further details, https://www.lovegranada.com/alhambra/
The districts of Albaicín and Sacromonte are worth a walk along their sinuous streets. The Albaycin, located opposite to the Alhambra, offers a unique view of the Palace, especially in the evening. The Mirador de San Nicolás offers one of the most wonderful sunsets in the world. The Sacromonte is famous for its flamenco shows in gypsy caves, a unique spectacle offered in Granada. The Sacromonte is also home of the Sacromonte Abbey, a historic building located in a privileged environment with views above both Granada city and Sierra Nevada (https://www.lovegranada.com/monuments/sacromonte-abbey/)
Granada Charterhouse (Spanish: Cartuja de Granada) is a Carthusian monastery, one of the finest examples of Spanish Baroque architecture. The charterhouse was founded in 1506. While the exterior is a tame ember in comparison, the interior of the monastery's is a flamboyant explosion of ornamentation. Its complex echoing geometric surfaces make of it one of the masterpieces of Churrigueresque style.
For further details: https://www.lovegranada.com/monuments/cartuja-monastery/
The Parque de las Ciencias is an interactive museum, of more than 70,000 m2, placed a few minutes from the historical center of Granada with one of the most varied offers of Europe's cultural and scientific leisure (www.parquedelasciencias.es).
You can find more information in the official tourism webpage http://en.granadatur.com/ and this web that includes a lot of information and tips on what to do in Granada to enjoy your stay here https://www.lovegranada.com/granada/things-to-do/
And don’t forget to enjoy Granada’s wonderful gastronomy (https://www.lovegranada.com/food/)!!