Undertown

Undertown is a subterranean alien city under Earth. It is one of the major settings for Ben 10: Omniverse. Undertown is an underground alien settlement where many kinds of alien species live and thrive below Bellwood.

History
According to Derrick J. Wyatt, after the Way Big fight in Destroy All Aliens, a large section of Bellwood was destroyed, an alien labor force was secretly brought in to rebuild the city faster than humans could do alone. During this construction, the alien laborers and their families built what started out as a very small camp in the caves beneath Bellwood. This camp grew over the years until it was the size of a city itself.

In The More Things Change: Part 2, Ben first discovered Undertown when he and Rook pursued Bubble Helmet, Fistina, and Liam underground after defeating them at Mr. Bauman's store. Ben discovered that Psyphon had been using Undertown as a base of his racketeering operations. Ben ended up fighting Psyphon, Bubble Helmet, Fistina, Liam, Thunderpig, and other unnamed henchmen of Psyphon while fighting Buglizard. After Ben fought off Buglizard, Psyphon and his followers were arrested by the Plumbers.

In Hot Stretch, Ben and Rook follow Ester to a deeper section in Undertown where the Kraaho made plans to make Earth hotter for them to survive and live in.

In Special Delivery, Ben made deliveries for Mr. Baumann to multiple citizens and businesses of Undertown in compensation for unintentionally destroying his property. During which, he ended up unraveling a secret auction held by Psyphon, and foiled his plans.

In The Frogs of War: Part 1, the town was revealed to humans for the first time, as frightened Undertown citizens launched through the asphalt, and left Earth in search of another home.

In The Frogs of War: Part 2, the residents of Undertown return to fight off the Incurseans and work with the humans side-by-side, stating that they'll work living together in Bellwood.

Known Locations

 * Of_Predator_part1_62.pngey T. Hokestar's Wagon
 * Blarney T. Hokestar's store
 * Lair of the Kraaho
 * Lair of the Vreedle
 * Pakmar's
 * Toilet Emporium (destroyed)
 * Pet Shop (destroyed)
 * China Shop
 * Loofah Emporium (destroyed)
 * Yarn Emporium (destroyed)
 * Lamp Store (destroyed)
 * Juice Bar (destroyed)
 * Alien Salon
 * Gas House
 * Y-it's Scooter Rentals
 * The Black Hole
 * Spaceman's Wharf
 * Sock Store
 * Tentacle Store
 * Mr. Smoothy Store
 * Pyroxivor's place
 * Soccer field
 * First Bank
 * Tournament Hall

Notable Inhabitants

 * Nosedeenians
 * Kraaho
 * Seebik
 * Lackno
 * Loovis Slerdlerk
 * Ester
 * Kinecelerans
 * K8-E
 * ML-E
 * N-8
 * N-D
 * L-N
 * J-NE
 * ML-E's Mother
 * Floraunas
 * Pax
 * Lepidopterrans
 * Lepidopterran Kid
 * Nemuinas
 * Lillimusha DiForestini
 * Acrosians
 * Fistina
 * Vreedles
 * Octagon Vreedle
 * Rhomboid Vreedle
 * Ma Vreedle
 * Dodecahedron Vreedle
 * Pretty Boy Vreedle
 * Maxatomars
 * Billy
 * Piscciss Volanns
 * Piscciss Volann Prisoner
 * Atrocians
 * She-Worst
 * Green-Worst
 * Purple-Worst
 * Violet-Worst
 * Slim-Worst
 * Pink-Worst
 * Orange-Worst
 * Blue-Worst
 * Members of Liam's Species
 * Liam
 * Chicken Alien
 * Ickthyperambuloids
 * Gil Steptoe
 * Squid-like Aliens
 * Vaxasaurians
 * Unknown species
 * Argit
 * Rad Dudesman
 * Pakmar
 * Blarney T. Hokestar
 * Sunder
 * Tentacle Vendor
 * Psyphon
 * Tummyhead
 * Bubble Helmet
 * Thunderpig
 * Sweet-Eels Sparklefunk
 * Solid Plugg
 * Pickaxe Aliens
 * Toby Monitor
 * Sock Vendor
 * Cow Alien
 * Bouncers
 * Unnamed Thug
 * Unnamed Thug
 * Unnamed Thug
 * Medic
 * Trumbipulor
 * Captain Kork
 * Alien Kid
 * Smoothy Vendor

Notable Visitors

 * Ben Tennyson
 * Rook Blonko
 * Khyber
 * Zed
 * Vulkanus
 * Gorvan
 * Michael Morningstar
 * Raff
 * Inspector 13
 * Nyancy Chan
 * Exo-Skull
 * Max Tennyson
 * Magister Patelliday
 * Gwen Tennyson
 * Kevin Levin
 * Looma Red Wind
 * Joseph Chadwick
 * Sir Morton
 * Twin Knights
 * Forever Ninja
 * Jimmy Jones
 * Albedo
 * Phil Billings
 * Will Harangue
 * Julie Yamamoto
 * Hervé
 * Ship
 * Zak Saturday
 * Doc Saturday
 * Drew Saturday
 * Fiskerton Saturday
 * V.V. Argost
 * Dr. Animo
 * Munya
 * Frankencryptid
 * Zombozo
 * Trumbipulor
 * Fistrick
 * Dr. Psychobos
 * Sevenseven
 * Eighteight
 * Bill Gacks
 * Rayona
 * Attea
 * Nyancy Chan
 * Kraab
 * Deefus Veeblepister
 * Simian
 * Gracklflint
 * Billy Billions
 * Mazuma
 * Captain Nemesis
 * Kangaroo Kommando
 * Chrono Spanner
 * Eighteight
 * Sixsix
 * Malice
 * Bahrvad
 * Slix Vigma
 * Yetta
 * Parts Dealer
 * Clyde Fife
 * Kyle Monitor
 * Kundo
 * Rook Shar
 * Rook Ben
 * Sheriff Wat-Senn
 * Mr. Baumann
 * Sheelane
 * Rojo
 * Jarett
 * Skurd
 * Professor Paradox
 * Eon
 * Eon's Servants
 * Ben 10,000

Ben 10: Omniverse

 * The More Things Change: Part 1 (first appearance)
 * The More Things Change: Part 2
 * Have I Got A Deal For You
 * Hot Stretch
 * Of Predators and Prey: Part 1
 * Of Predators and Prey: Part 2
 * Many Happy Returns
 * Gone Fishin'
 * Ben Again
 * Store 23
 * Special Delivery
 * Showdown: Part 1
 * The Frogs of War: Part 1
 * Rules Of Engagement
 * Return to Forever
 * The Ultimate Heist
 * A Fistful of Brains
 * Max's Monster
 * Bengeance is Mine
 * Catfight
 * Collect This
 * The Vengers
 * Cough It Up
 * The Rooters of All Evil
 * No Honor Among Bros
 * Universe Vs. Tennyson
 * Clyde Five 
 * Rook Tales
 * Charm School
 * The Ballad of Mr. Baumann
 * Breakpoint
 * Color of Monkey
 * Vreedlemania
 * Stuck On You
 * Let's Do the Time War Again

Trivia

 * According to Derrick J. Wyatt, Undertown has been underneath Bellwood since sometime fairly after Ben 10: Destroy All Aliens.
 * After Bellwood was wrecked in Destroy All Aliens, the Plumbers secretly brought in alien labor for the fastest possible reconstruction. These alien laborers and their families settled in the caves beneath Bellwood, in what has now become Undertown.
 * As of A Jolt from the Past, Undertown is, at least partly, powered by a volunteer group of Megawhatts who were freed from imprisonment by Ben and Rook.