Where are the HL2 Maps Located?

Garry's Mod general
#1

Hey I am working on a HL2 multilayer game mode for Garrysmod, and I need help finding where the HL2 maps are located. All help is highly appreciated!

#2

In the GCFs.

#3

Oh ok thanks! I feel dumb. How do I extract them?

#4

Use GCFScape.