Ending a Portal map
Using this tutorial you can end maps like on Portal's Bonus maps.
Create a brush that's the area that you want the map to end. Texture it with a "tools\toolstrigger" texture. Select it and press CTRL+T. make it a "trigger_once".
Make two entities. Make a "point_clientcommand" and call it "end_disconnect". Make a "env_fade" and call it "end_fade". You may want to place these entities next to the trigger_once brush for convenience.
Make the trigger_once's outputs the following:
|Output named||Target entities||Via this input||Parameter||Delay|
When you touch the trigger the "env_fade" will make you start to fadeout. After 2 seconds, the fadeout will be complete and the "point_clientcommand" will make you return to the main menu.