The formation of droplets from water vapor in the presence of condensation nuclei is the most familiar example of gas-to-liquid transition. Detailed understanding of this process is of fundamental importance not only in the basic scientific field but also in the fields of meteorology and environmental science, because needless to say, it is the process that causes precipitation. Although numberless studies have been made since more than a century ago , there still remains a lot to be done to elucidate this process going on in the atmosphere . One of the reasons for this is that most laboratory studies can not attain a scale large enough to reproduce various conditions characteristic of the actual environment. On the other hand, field studies can afford us information relevant to the real scale. However, it is often extremely difficult to deduce a general understanding from field data because of the inevitable diversity and non-reproducibility of experimental parameters. One of the conceivable ways for overcoming these situations is to scale up the lab experiment to approximate the real conditions. This paper reports a few primitive results from such an experimental trial. In this study, we used a semi-real scale experimental system, the main part of which is a long vertical shaft. The length of the shaft was 430 m, so the experimental scale was closer to the real one than in any previous lab studies. By generating an updraft with moisture, we observed the formation of clouds and examined the number and size of cloud droplets together with temperature, humidity, and wind speed. Thus we were able to approach the actual conditions in a well-defined and reproducible manner and to obtain some novel information on cloud formation.