Goblins are some of the most industrious builders and miners among the humanoid races. Many a goblin force will make it's home in dwarves halls won after decades long wars buthere are unique features that will define goblin mines and halls as well.
Goblins mine the riches of the earth as greedily as the most selfish of dwarves ever could and have developed mining techniques in advance of those practiced by many mannish nations. Goblin mines seldom stay a place for ripping forth riches secreted in the earth and often become seats of industry and and dwelling place.
Large chambers and caves breached in a goblin mine will be ringed with walkways carved in stone or made of propped up woodworks. These woodworks will sometimes be rather elaborate networks of bridges and platforms offering guard posts and living space for the goblins.
Goblins appreciate natural beauty in an odd way, when the cruelty of the world and rot are present goblins find the most beauty. Their mines will sport spiked grottoes and gardens of colorful fungi.
Identified as simple peasants as wells these are in fact shafts used by goblins to travel to the surface and to provide ventilation to their mines and halls far beneath the ground.
Take heed when entering a goblin well to plumb it's depths they are often trapped and monitored by secreted guardians that can send one tumbling to their doom with a hand that seem to appear out of nowhere.
A Goblin hall may start as a modest gathering point for a tribe guarded by a simple gate but in time it will grow into a grand subterranean hall festooned with frescoes and grand vaulted chambers with ceiling held up high overhead by baroque decorated pillars. Many a decoration conceals a secret passage, spy-point, or murder hole. The Pillars that stretch high overhead will offer amble holds for goblins to stream up and down to either escape by trapdoors high overhead or to spill forth in great numbers upon invaders to the hall.
Goblins frequently construct balconies and ledges that ring their halls where they can rain down their wrath upon invaders.
Stairs will often be seen with no rails running long ways along the walls of a grand goblin hall, these stairs offer easy travel for those of goblin stature and gait but are tricky and dangerous for those of mannish size or dwarf girth and sometimes dangerously trapped. Goblins are not prone to construct sheltered stairwells as they prefer to be bake to monitor ascents and descents with troops of archers.
Most daily life will take place in the hall with all but the most elaborate or noxious industries being practiced in the same space the goblins dine and train within.
Goblin sleeping halls will be secreted off of their halls and will be empty and silent during sleeping periods.
Goblins do not restrain themselves to the limits of what is practical and will slave away (or ensure their captive do) to surround their grand halls with elaborate and often impressive entry chambers that rival the halls of mannish emperors.
Goblins will build wide and high interlocking tunnels crisscrossed by ridges and sometimes running alongside each other appearing to be insets and ledges. Many a tunnel will reach a dead end seemingly for no rational purpose or lead directly into a shaft with no stair.
Goblins will also add crawl ways to allow guards and those trusted by their ruler to spy on the goblin tribe itself in secret and offer mysterious access between chamber, tunnels, and halls.
Not all of the works of goblins are beneath the surface (see Goblin Wells above) as they will often encircle the entrances to their dwellings with walls of throned hedges. These hedges will grow to be impenetrable hard to burn walls over the centuries and will sometimes be grown in difficult to navigate maze-like patterns.
Goblins not wanting to let mankind and other show them up on the surface will from time to time contract towers of stone. These stones will come deep from their mines and halls beneath the ground and are often (but not always) a clue there is a large goblin settlement nearby. These towers seldom allow entrance on the ground either offering access part way up the tower -side or from secreted passages scattered about the tower tunneling down and then up into the tower itself.
Goblin towers are often hollow in the center with rooms and passages ringing a greta central shaft that may descend deep into the ground beneath.
There are few windows or arrrow-slits in a goblin tower as they favor sheltered turrets and balconies where they can step out and pour death on those beneath while thwarting the advance of sunlight as much as they may manage.
Goblins are a pretty magical race but do not often sport spells as human wizards do, their magic while not often noticed will be woven into their construction offering spaces larger than would seem natural, doors that link rooms with no adjoining walls and steps that travel to spaces no incline should reach.
Magical traps and illusionary walls may be as common as in a mad wizard's labyrinthine deathtrap.
Tread carefully while entering the domiciles of goblins and do not imagine all that you see is all there is at hand.
Goblins got ignored somehow way back when I was covering the constructions and habitations of Orcs, Kobolds, Gnolls, and Hobgoblins. I had to correct that error.