HL2 skyboxes

[Mister.K]

I found out that many 2001 maps doesn't have skyboxes and instead, they have these building getting smaller brushes.
Is it because at that time HL2 was like HL1?

[Spicy]

It's a 3D skybox. it gives the illusion of a bigger world.

[Mister.K]

It's a 3D skybox. it gives the illusion of a bigger world.

Does this old skyboxes look wierd if i combine it with sky_camera retail skyboxes