Post your best photos of waterfalls.
In 1980 there was a movie called "The Final Countdown" where an aircraft carrier was transported back in time to Pearl Harbor. In one scene, F-14 Tomcats zoom by WW II Japanese Zeroes, to the astonishment of their pilots.
In this contest, create similar scenarios with other times from history. Is a modern tank fighting the ancient Hittites? Is a spaceship from the future fighting in WW II? But, it can go both ways. Are Vikings attacking modern day London? Have some fun with history!