National Astronomical Observatory of Japan held its 2006 Open Day at Mitaka Campus. This year, ALMA-J Project Office presented: explanation of ALMA using poster exhibition and a miniature of the ALMA site; mini-lectures by six lecturers; celestial journey in the Chilean skies using a constellation camera at the Operations Support Facility of ALMA; a mini-experiment to see if rubber balls fallen from a higher place (to resemble radio waves from the universe) are collected into the focal point of an antenna dish; and another experiment to receive satellite broadcasts using a lid of a pot, instead of an antenna dish. The Advanced Technology Center, which the receiver development team of ALMA belongs to, introduced their development status, in addition to their annual attraction, distribution of helium-filled balloons. The picture shows children trying to control the constellation camera in Chile remotely via the Internet. In the afternoon after the moon went down, visitors could enjoy a celestial journey in the southern sky with Large and Small Magellanic Clouds and the Southern Cross.