The world’s highest tennis court stands atop the fourth highest hotel in the world - Burj al-Arab at Dubai. The tennis court is circular in shape and when no session is at play, it doubles as a helipad. The exact height of the tennis court is not known, but the hotel is 321 m (1,053 feet) tall and the court is located very near the top. My guess is, it’s close to 1000 feet.
In 2005, when Roger Federer and Andre Agassi were at Dubai for a tournament, they were invited to play a few rounds at the Burj’s helipad-converted-tennis court.
Looks like they lost the ball.