the best inspiration 4 hl mapping is... Created 20 years ago2003-10-03 18:43:11 UTC by ministeve

hl. use the noclip 2 find out how hl was made. 4 instance. final battle. when u get teleported in2 the big room with a jump pad and an underwater bit twice, a garg appears. where did it come from? a box outside with the AAATRIGGER texture. teleported in the 2nd time u visit the room. the nihlanths teleport is complicated and how they did it is way beyond me but take a look around. try 2 find out how exactly the screen turned green when we teleported. it really helps make maps.
sayonara.

yea, but make sure you are not trying to copy othe people's work exactly.. most players will spot the clone immediately.. try this site for some inspiration :

http://www.abandoned-places.com/

oo.. almost forgot.. if you are going to use any of the pictures in your levels, make sure to credit the photographer
(i think his first name is Henk)