Recommended:

OS: OSX 10.7.5 or newer
Processor: Intel chipset
CPU Speed: 2.0 GHz
Memory: 512 MB RAM
Hard Disk Space: 3.5 GB free disk space
Video Card: (ATI): Radeon 9600 Video Card (NVidia): GeForce FX 5200
Video Memory: (VRam): 128 MB RAM
Multiplayer: Internet (TCP/IP) and LAN (TCP/IP) play supported. Internet play requires broadband connection.
Media Required: DVD Drive Supported Video cards: NVIDIA GeForce 5200, 6600, 6800, 7800 ATI Radeon 9600, 9650, 9700, 9800, X600, X800, X850, X1600
NOTICE: This game is not supported on volumes formatted as Mac OS Extended (Case Sensitive).

Sid Meier's Civilization IV screenshots