Although we've already seen many frozen sculptures and structures, designer Brent Christensen's impressive Ice Castles are as tall as 20 to 25 feet, and use only icicles as their building material. The artist uses water to attach and mold thousands of icicles together, ultimately creating giant structures that even include stairs, tunnels, and archways on their interior. Christensen creates his own icicles on a rack that produces up to 5,000 pieces in a day, which are then transported to him by his crew members. Each castle requires millions of gallons of water in order to reach its massive height and size and are illuminated with LED lights in the evening.

[via MyModernMet]