Columbus, Mercator, and Humboldt are of great importance for the development of the modern geography, each of them with a special contribution.
Columbus managed to physically discover two new continents previously unknown in the Old World, thus increased the knowledge of the size and territories of land on the Earth.
Mercator was revolutionary with his projections of maps which were by far the best and most precise, thus allowing the people to be able to see the world much more accurately.
Humboldt was a scientist that set the foundations of biogeography with his study of botanical geography, and also laid the foundations for the geomagnetic and meteorological monitoring which is of great importance of the daily life of the people around the world.