Bring your passport
For some reason we were thinking it was like any other European country we have been to and thought you just breeze on by the boarder. Not! You do need your up to date passport to enter Gibraltar and return to Spain. It is a pretty painless boarder crossing, providing you have the correct paperwork.
Look out for furry little pickpockets
The monkeys up in the Nature Reserve are very crafty and not afraid you in any way. If they even slightly hear the rustling sound of a bag or see something colourful sticking out of your pocket, they will flock you. We were just casually walking past a bunch, alongside the road, and one reached into our pocket and pulled out the bottle of coke! We retrieved it, but they are quick and sly.
Don't be surprised if you get an unexpected hitchhiker
The monkeys in the Nature Reserve also like to hop on your car and go for a ride. If you are near the souvenir shop at the cave, you may even have them hop directly on YOU!
Gibraltar has their own money and it is the Gibraltar £, same exchange rates as the British £. If driving, have some Gibraltar £ available to pay for parking meters as well as the parking garages. The garages aren't manned and they only have machines to pay for your ticket, these machines only take Gibraltar £. No credit cards or Euros are accepted in many of the parking garages, but they are in many shops and restaurants.