Have not seen that particular pic but from the carriage (That pic I feel is photo shopped) it appears to be Gustav 80cm rail gun used in the seige of Sevastopol in WWII it fired 2 types of shells a 5 tonne and 7 tonne from memory the 7 tonne shell could be hurled 19 miles it was made by Krupp, one shell penetrated 100' of earth to destroy a Russianammunition dump. It had a mate Dora same configuration info can be found on Google about them. They were white elephants and required a crew of 1300 men to man, lay the tracks for the firing site and man the beast/air defense batteries etc. The tracks were laid in a curve so the piece could be aimed as it had no traverse on it it weighed @1200 tonnes. The Bovington tank museum in England
has one of its 7 tonne projectiles.