When the area around Karasuma Junior High School was excavated during the construction work of the Karasuma Line of the Kyoto City Subway, bedrock was found, making the construction more difficult; when the underground bedrock was studied through geophysical prospection, it turned out, however, that an underground mountain slopes down southeastward.
地下鉄京都市営地下鉄烏丸線の工事のときに烏丸中学校付近を掘削したところ、岩盤が発見されて難工事となったが、この地下の岩盤を物理探査法を用いて調査したところ、地下山脈が南東方向に存在することが判明。