The Hall of Diplomacy was a governmental and cultural building in the capital city on the Kreetassan homeworld, Kreetassa. Outside the Hall were a stand of Alvera trees which, by 2152, were over 300 years old and which the Kreetassans considered a cultural treasure.
In 2152, Porthos urinated on one of the Alvier trees outside the Hall of Diplomacy. Upon revisiting Kreetassa shortly thereafter, the dog's owner, Captain Jonathan Archer performed ritual sectioning of an Alvera tree – required by the Kreetassans as an apology – outside the Hall. (ENT: "A Night in Sickbay")