Barcelona is possibly the teams' favourite test track in Europe at the moment. I love the track. At McLaren, my nickname was the Barcelona Bullet - I was quick there because I knew how the track would evolve during the day. Here is why I think teams keep heading back to the Circuit de Catalunya.
COMBINATION OF CORNERS
One of the main reasons it works so well as a test track is the combination of corners. Modern F1 tracks designed by Hermann Tilke do not feature long, constant-radius corners. They are slow-speed, 90-degree or hairpin turns.
Barcelona is an old track designed originally for motorbikes, so most of the corners have a long radius. You're in a corner for a long time and that helps you feel the car balance, which in turns helps with set-up.