Paul Gregg really wanted to make something that his grandkids will enjoy. This spurred him to start on a project to build roller coasters in his own backyard. 

It's not something that's too difficult for the retired aerospace engineer. In two years, he managed to build three different rides in his backyard. 

Have a look at the roller coasters that he built:

As expected, his six grandkids look forward to spending the day at his place all the time now!

Cover image from Coaster 101

*Article source: Sunny Skyz