Go see El Morro, and walk up the hill that Teddy Roosevelt rode up. Go to Barrachina's and have a pina colada. If you have time, do not miss the rain forest. Stay in a hotel on the beach. Best restaurant in town, Marmalade, is fantastic, and the owners come to chat with you. $75 per person and worth every cent.
If you have missed Diamonds International or Little Switzerland in other Caribbean ports, this is your chance. Actually, there is nothing worth buying that you can't get from a reputable source on the net. Easy walk to and from the ship.
Nice tour halfway up Mt. Teide. Interesting rock formations; you are above the tree line and there is not much vegetation at the highest point the tour takes you.
Not much to do in town; many of the same as in Caribbean ports.
Interesting fortifications. You do not need to go to the end.
Rock of Gibraltar Rating:
Do not miss this. Take a private tour or use a cab as they can get higher. The apes will jump on you and your car. You can see Africa. Did I mention the apes?