Evil Genius FAQ

Outside:
  There are several objects that go outside.  Hotels and Topside Shacks create
  space you can create other rooms inside.  Hotels only allow you to create 
  hotel-type rooms, topside shacks let you create anything in a 3x2 space.

  Topside shacks become available when you get your control room running.  They
  are expensive and provide only a small space, so what's the point?  There's
  a whole section on things to do with a Topside Shack if you find yourself
  with too much cash on your hands.

  Evil Base Entrance - Creates a door into the mountain, you start with one. 
  Camouflaged Door   - Goes on top of an Evil Base Entrance
    Note: It won't allow placement if there's a regular door just past the
    evil base entrance.  Move the other one farther back.  The camo door 
    also counts as a door; you can assign it a security setting and agents
    must bypass it to get into your base.
  Cameras            - Supplement your base security system, great for 
    tagging mad tourists for weakening.  Agents will blow up the non-disguised
    version occasionally.
  Sentry Guns - Automatically fire on tagged intruders, can shoot to capture
    These have a short lifespan, they generate high heat and agents love to
    attack them.  You get no notice of this.  I'd suggest building them only
    when you're willing to keep a henchman near it to protect it till the
    disguised version becomes available.