Games like Polyion
Games like Polyion include Cities: Skylines, Planet Zoo, Cities: Skylines II, PC Building Simulator, and Planet Coaster. We matched them by the tags players give Polyion on Steam (Management, Sandbox, City Builder, Building, and Immersive Sim): closest matches first, and among equally close ones the better-known games.

Cities: Skylines
Shared: City Builder · Management · Building

Planet Zoo
Shared: Management · Sandbox · Building

Cities: Skylines II
Shared: City Builder · Sandbox · Management

PC Building Simulator
Shared: Management · Simulation · Building

Planet Coaster
Shared: Management · Sandbox · Building

Planet Coaster 2
Shared: Sandbox · Simulation · Building

Two Point Museum
Shared: Building · Simulation · City Builder

SimCity™ 4 Deluxe Edition
Shared: City Builder · Sandbox · Immersive Sim

Foundation
Shared: City Builder · Sandbox · Management

Prison Architect
Shared: Sandbox · Building · Simulation

Let's School
Shared: Management · City Builder · Sandbox

Timberborn
Shared: City Builder · Sandbox · Management

Two Point Hospital
Shared: Management · Simulation · Building

Jurassic World Evolution
Shared: Management · Building · Sandbox

Kingdoms and Castles
Shared: City Builder · Management · Sandbox

Two Point Campus
Shared: Management · Building · City Builder

Jurassic World Evolution 2
Shared: Management · Building · Sandbox

Manor Lords
Shared: City Builder · Management · Simulation

House Flipper
Shared: Simulation · Building · Sandbox

Planet Zoo 2
Shared: Sandbox · Simulation · City Builder

The Universim
Shared: City Builder · Sandbox · Management

Transport Fever 2
Shared: Management · Simulation · City Builder

Townscaper
Shared: Sandbox · Building · City Builder

Settlement Survival
Shared: City Builder · Building · Management