Gran Canaria is often described as a continent on an island, and truly it offers huge diversity of landscape, with volcanic mountains towering above thick forest, and of course the famous desert in the south of the island, where you can ride camels, and explore in a 4WD vehicle.
The main city of Las Palmas is the largest city in the canaries, and has a wide variety of museums and art galleries, as well as plenty of international restaurants and bars.
Lanzarote is a dry place where there is hardly any rain, although the island has some great resorts and attractions, the main draw is the UNESCO Biosphere reserve Parque Nacional de Timanfaya, where the remains of a giant volcanic eruption some 5000 years ago have left the landscape bare, and given the area an other worldly feel that has made it the set for many science fiction films.
Santa Cruz de Tenerife is the capital of the islands, and the busiest port for cruise ships visiting the Canaries.
It is a bustling town with several well-preserved Baroque buildings, and tonnes of souvenir shops nearby. If you are staying in Tenerife, then it's a great place to go out shopping or for the evening.
