A large office building and clacks tower on The Tump in Ankh-Morpork. It serves as the corporate headquarters of the Grand Trunk Semaphore Company. The heights of the Tump Tower offer magnificent views of Ankh-Morpork, in noted contrast to that of the Patrician whose own office view was being more obstructed by Grand Trunk's clacks towers.
An obvious play on America's "Trump Tower". It also refers to the common practice of placing communications antennae on skyscrapers and tall office buildings.