There is a bar between the cattle and the mine, to the back of which you'll find a set of stairs leading to the goblin dungeon. Through the cellar (a popular place to AFK melee skills) and past some goblins and pitcher plants, you'll encounter the Goblin Pollinator. After taking the Pollinator down to half life, he reveals the hidden passage which leads to the Goblin Matriarch.
Past the Matriarch are barrels that drop semi-precious quartz crystals, which can be sold for argents at the banker. Barrels throughout the main level also drop wine and chardonay, which are great heals.
The Pollinator drops random gear (got a Darkling Slayer staff while taking these screen shots!). The matriarch drops 800+ argents and drops random gear.
Chests in this level vary between 10 and 30.