Shack

Dr. Horn has a secret shack hidden away in the map Surface Tension. It has become known as the "taco shack" because of the fact that there is a plate with three tacos on the desk inside the shack, and another plate with a taco on the picnic table outside. Pizzas are nowhere to be found.

Getting there
map bm_c2a5c sv_cheats 1;noclip;setpos -12345 -13995 6738;noclip
 * Just "noclip" will not work to get here. You need to "env_remove reload" first.
 * There is a button on a console on the cliff side that must be pushed to reveal the cave entrance to the shack. It will turn yellow and indicate an 'error' when pressed. After pressing it, back-track and drop down a few ledges to find a small cave with a portal inside. When you enter the portal you will teleport to a location outside the shack.
 * Alternatively, you can type the following commands into the console to get there:

How did Dr. Horn get there?
Dr. Horn (and any visitors) entered the shack area by climbing down a rope. The rope can be seen hanging down the rock wall opposite to the shack entrance. The incoming and outgoing portals are anomalies which most likely were created as a result of the resonance cascade.

Contents

 * Dr Horn's picture.
 * A screen that shows a Hammer window open with a wireframe display of the Anti-Mass Spectrometer.
 * Tacos.
 * An aeronautical chart with an airport diagram tacked onto it.

Hidden texture

 * When viewing the interior of the shack in Hammer, an overlay texture, which for some reason doesn't render in-game, can be seen on the wall. The texture shows a collage of airport/airplane photos. The larger one seems to be an aerial photo of a military heliport in Chengdu, China (Google maps link).
 * Dr Horn's shack seems to be the only location this particular texture is used in the game.
 * The texture is stored in the file materials\decals\papers\photos2.vtf.

Shack exterior and surrounding area

 * There are two satellite dishes on the roof/wall.
 * On the wall next to the door, there is a no trespassing sign and a camera prohibited sign.
 * Outside the shack there is a picnic bench with three plates on the table and some leftover food items.