Cities: Skylines - Deluxe Edition Upgrade Pack

Summary pulled directly from Steam - Some text may only be applicable to Steam platform

The Deluxe Edition:

Included in the Deluxe Edition are 5 In-game historical monuments from around the world, the games original soundtrack as well as a digital art book.

Five in-game items include:

Statue of Liberty
Eiffel Tower
Brandenburg Gate
Arc de Triomphe
Grand central terminal

Original Soundtrack:

This Original Soundtrack includes 14 unique tracks mixed from the ambient music of the game, allowing you to enjoy the wonderful music whenever you want.

Digital Art book:

See the concepts behind the buildings! The book features almost a 32 hand drawn concepts of the game various buildings and the story behind each.