That dark thing sticking out into the ocean (about halfway up from the bottom of the photo) is half the runway at Gibraltar International Airport. As you can see, the visible half was built on reclaimed land, but that’s not the strange part.
This is the strange part:
The international border between Spain and Gibraltar is on the Spanish side of the runway. After they check your passport and wave you through, you enter Gibraltar by walking or drive directly across the runway.
They close the gate when a plane is ready to take off or land, and traffic and pedestrians queue up. When it’s clear again, they open the gates, and masses of vehicles and pedestrians scurry across the runway and into Gibraltar.
It’s very odd when you realize that you’re in the middle of the runway at an international airport.