Secret Deep Underground Structures Revealed By Google Maps

There appears to be a glitch in the hiking (and biking) function of Google Maps. The topographic chart on the bottom left occasionally shows sudden and deep drops in altitude, although there is nothing on the map that would indicate such. As it turns out, these glitches reliably appear in locations with known underground structures like tunnels or bunkers. Some of these structures are open to the public, others are not. These glitches appear worldwide and strangely also in locations with no known underground structures....