This is my first time making a complete level for Half-Life 2, and first level design project. It's only around 5-10 minutes of gameplay.
To install just extract the map file in:
C:\Program Files (x86)\Steam\steamapps\common\half-life 2\hl2\maps
Then open Half-Life 2, bring up the console and type:
map hl2_metro
And you're good to go!
I welcome all constructive criticism. This level is a summary of what I've learned so far about Half-Life 2 mapping and level design in general. I will be working on a longer one next time around.