My instantaneous thought when reading of the Syrian Golan-1000 multiple-rocket-launcher was the German World War Two "Karl" siege mortar. Karl having a bore of 24 inches [600 mm] and firing a round of prodigious size.
"'Karl-Gerät' . . . was a World War II German self-propelled siege mortar designed and built by Rheinmetall. Its heaviest munition was a 60 cm (24 in) diameter, 2,170 kg (4,780 lb) shell, and the range for its lightest shell of 1,250 kg (2,760 lb) was just over 10 km (6.2 mi). Each gun had to be accompanied by a crane, a heavy transport trailer, and several modified tanks to carry shells."
See this You Tube video of a Karl as being fired in combat at the Siege of Sevastopol, WW2.
"Seven guns were built, six of which saw combat between 1941 and 1945. It was used in attacking the Soviet fortresses of Brest-Litovsk and Sevastopol, bombarded Polish resistance fighters in Warsaw, participated in the Battle of the Bulge, and was used to try to destroy the Ludendorff Bridge during the Battle of Remagen."
Read from the wiki that instance of "Karl" as was used by the German during the Battle of Warsaw, 1944. Damage as done perhaps quite similar to the destructiveness of Golan-1000? A whole city block of an urban area reduced to absolute rubble with a single shot. Golan using a thermobaric detonation as opposed to the "Karl" high-explosive but the result more or less the same.