Strange clouds over "Naval Εastern Mediterranean Command" HQ

Take a careful look at these pictures. The white lines leading to the central cloud could be a creation of mother nature, some could think. However, one should note, how the central cloud seems to "swallow" the smaller clouds. This weird atmospheric scenery occurred in the sky above Agia Paraskevi, suburb of northern Athens, where the headquarters of Greek Naval Εastern Mediterranean Command HQ (SDAM) is also located. SDAM, established during the Cold War era in 1955, has standards for nuclear and biological warfare.

The pictures were shot on January 15th 2013 from Messogion Avenue, the street that divides the suburb into two.

Conclusions and questions are yours...