CASTIA is a software package able to check radio source visibility at a given date from a collection of international facilities. The tool outputs plots containing the visibility and the elevation of radio sources versus time. A special mark is used for the transit time and visual warnings are present when the azimuth rate is beyond the recommended limit or superposition with the sun/moon occurs. The query can be done by source name, sent to the SIMBAD name resolver for finding the corresponding right ascension and declination, or by giving coordinates for a single source or for a group of targets.