Inkwell Ideas has developed three key apps to assist in building a diverse world. Worldographer (AKA Hexographer 2), Cityographer and Dungeonographer. A great value with some fantastic options and excellent auto population features for NPC’s.
ProFantasy has an entire suite of software dedicated to creating worlds, cities and dungeons. Although a bit pricey, the software is very detailed and puts the creative control at your fingertips to immerse your players in a diverse world.
This is a really nice online based software with a Pro version at $5 a month or $25 a year. Make your World, Kingdom and Cities in great detail. In order to get off to a good start, I would recommend watching a YouTube video or two.
Free is a very good price! Generators for Worlds, Towns, Names, Dungeons, Treasure, Weather, Encounters, Quests, NPC’s and many more. There are spell sheets, initiative trackers and other helpful items.