Believe it or not, there are olive trees in the middle of Madrid. They endure the traffic, the crowds, the pollution...and are thriving! These are planted in front of the International Olive Oil Council headquarters. Each one (there are 15) has a plaque indicating the country of origin (Italy, Portugal, Tunis, Morocco, Greece...) and the date of plantation. The first of them, the spanish one, was planted in 1992 by H.M. King Juan Carlos; the last one came from Morocco in 2004. The sculpture in the front represents, of course, the dove of peace with the olive branch.
I recommend you to visit the International Olive Oil Council webpage; you'll find there everything you wanted to know about olive oil but were afraid to ask.