If you want a custom terrain, you'll need to download a terrain that you like. You can pick one from the list below. These terrains are modified so you can replace the default dota terrain with them.

[NOTE] All terrain files share the same password: terrain

TI5's Desert Terrain
https://sharemods.com/hnj04zzqn0od/dota_desert_739d.7z.html


TI6's Immortal Gardens
https://sharemods.com/3i0ftow6su34/dota_coloseum_739d.7z.html


TI7's Reef's Edge
https://sharemods.com/0hxilszv37d5/dota_reef_739d.7z.html


TI8's Emerald Abyss
https://sharemods.com/y90tfqm8h56d/dota_cavern_739d.7z.html


TI9's Overgrown Empire
https://sharemods.com/wo14jkqxkxkj/dota_jungle_739d.7z.html


TI10's Sanctum of the Divine
https://sharemods.com/3g5tslyvs8ag/dota_ti10_739d.7z.html


Crownfall
https://sharemods.com/nn4olqxxm3b4/dota_crownfall_739d.7z.html


The King's New Journey
https://sharemods.com/s5m9ojnax08x/dota_journey_739d.7z.html


Seasonal: Winter
https://sharemods.com/2mwy0rbtbv0g/dota_winter_739d.7z.html


Seasonal: Spring
https://sharemods.com/67bfiug0fxgn/dota_spring_739d.7z.html


Seasonal: Summer
https://sharemods.com/4tbv83ttkop6/dota_summer_739d.7z.html


Seasonal: Autumn
https://sharemods.com/d2lucrn0io8l/dota_autumn_739d.7z.html

[NOTE] You will need a file archiving program like WinRAR or 7zip to decompress the files.

Now we'll, browse to Dota 2's local files and go to:
then you will need to create a new folder depending on your game language, if you're playing Dota 2 in english, you may name your folder:
or else you will need to replace 'tempcontent' with the name of your language. Check the list in the bottom section of the guide if you're in doubt about the correct naming for your language
Depending on your language, the folder may already exist, then you may just use the already existing folder.

Inside the folder you just created (or not), you will need to create another folder, name it:
Extract 'dota.vpk' from the .zip file you just downloaded inside the 'maps' folder. The password for all terrain files is "terrain".

To make the game load the modded files, simply add this to your game's launch options if you're playing Dota in the English language:
If your Steam language is set to anything other than English then this launch option might not be necessary. But if you want to be safe you may still still use it, replacing 'tempcontent' with the name of the language of your choice.
Removing the command will make it load the default terrain again.

You may need to update your terrain file if Icefrog makes changes to the map in a future patch. I'll try to keep the links in this guide always updated so you guys don't have trouble with that.