Hub

A hub is a map which serves to connect many other maps together. The function of a hub map is analogous to the function of the overworld in a role-playing game. The overworld acts as an "in-between" area that connects individual dungeouns together in a nonlinear fashion. A hub does the same thing, except with the levels of a wad. The first Doom engine game to use a hub was Raven Software's Hexen. Hexen used the hub system to create puzzles that reqired the player to travel back and forth between levels in order to solve them. Strife was the second game to use the hub system. However some source ports such as ZDoom support hubs, allowing them to be created for either Doom or Heretic levels.

Doom hubs are difficult to create and implement and are therefore infrequently used. However, several prominent megawads have utilized them, including Team Future's RTC-3057 and TeamTNT's Daedalus: Alien Defense