What is the tallest mountain in the world?

Mount Everest
Mount Everest, located in Nepal and Tibet, is usually said to be the highest mountain on Earth. Reaching 29,029 feet at its summit, Everest is indeed the highest point above global mean sea level—the average level for the ocean surface from which elevations are measured.26 Feb 2021

This is all you, but i can give you some topics that you could try. if it rained when you want to do something outdoors, it 'limits' that human activity. maybe you want to do an experiment that goes throughout the whole year and you have to have above freezing the entire year. this 'limits' your activity. i thought of those just off of the top of my head. something that gets to me that might be getting to you is you are thinking too hard about what to do. think simply, and if it is too simple, then bump it up just a little bit.