  We report the discovery of periodic flares of 6.7GHz methanol maser in the
young massive stellar object G22.357+0.066. The target was monitored in the
methanol maser line over 20 months with the Torun 32m telescope. The emission
was also mapped at two epochs using the EVN. The 6.7GHz methanol maser shows
periodic variations with a period of 179 days. The periodic behavior is stable
for the last three densely sampled cycles and has even been stable over ~12
years, as the archival data suggest. The maser structure mapped with the EVN
remains unchanged at two epochs just at the putative flare maxima separated by
two years. The time delays of up to ~16 days seen between maser features are
combined with the map of spots to construct the 3-dimensional structure of the
maser region. The emission originating in a single ~100 AU layer can be
modulated by periodic changes in the infrared pumping radiation or in the
free-free background emission from an HII region.
