The Great Fire Of Ankh-Morpork was caused by Broadman the owner of the Broken Drum, when he tried to burn down the bulding after making an in-sewer-ans poly-sea with Twoflower that the Drum would not burn down. The Fire then spread to the rest of the city. It was eventually extinguished by closing the downstream River Gates, which were actual gates across the river. This ensured that the river, and also the contents of the river overflowed onto the lower parts of the city. This added a "particularly noisome flux" to the survivors' problems when they came to rebuild the city.