A military base is a rabbit hole building found in The Sims 3.

Gameplay description

Sims can go to a military base to get a job in the Military career, attend a Handiness class, or tour the base. It is possible to WooHoo on a military base, but not until after touring the base. Aliens^[TS3:S] can go sell extraterrestrial secrets to the military base between 6 AM and 8 PM, and the alien will be rewarded with some simoleons.

There is no military base in Bridgeport, Appaloosa Plains, Starlight Shores, Moonlight Falls, and Isla Paradiso. Sims who live in these worlds and are in the military career work in the City Hall, as it contains the Military Headquarters. You can add one via Edit Town, however most NPC's will still go to City Hall.

The bases in Sunset Valley, Twinbrook, and Roaring Heights have airstrips near them, and the base in Sunset Valley additionally have a space rocket launchpad.

Varieties

Fort Gnome Military Base in Sunset Valley

Fort Gnome Military Base in Hidden Springs (known as "H.S. Center of Defense" in Edit Town mode)

Fort Gnome Military Base in Barnacle Bay (known as "Building O' War" in Edit Town mode)

Fort Salas Military Base in Riverview

Sims in Arms Military Base in Twinbrook

Public Services Office in Bridgeport

Appaloosa Plains Civic Center in Appaloosa Plains

Grunt Military Base in Lunar Lakes

City Government Complex in Starlight Shores

Desert Arms Military Base in Lucky Palms

Mango's Military Base in Sunlit Tides

Commonwealth Court in Moonlight Falls

Civic Center in Monte Vista

Peaceful Protection Agency in Aurora Skies

Garda Police and Military in Dragon Valley

Civic Center in Isla Paradiso

The Just Us Justice Department in Midnight Hollow

Ocean's Edge Military Base in Roaring Heights

Camp Gnome Military Depot in Moonlight Bay

Camp Gnome Military Base in Moonlight Bay (upgraded variant)

City Hall in Sugar Maple Coast

Trivia

• The Grunt Military Base and Mango's Military Base are probably named after the Grunt and Mango families, respectively. This is considering both families are mainly involved in Military.
• At 5 AM, "Reveille" plays on the military base, however, it won't happen if the military base is inside the city hall.
• In The Sims 4: StrangerVille, there is a military base in the outskirts of StrangerVille. However, Sims cannot go there or interact with it in any way, as it is purely decorative set-dressing.
• The writing over the entrance of Fort Gnome, Fort Salas, Desert Arms and Ocean's Edge Military Base can be read as "strength and honor and guns" (and mirrored) in the alphabet used in The Sims FreePlay.