And you thought the Vikings stadium was a feat of engineering and construction might.

Golden Valley-based Mortenson Construction has constructed North America's tallest flagpole. Located at the Sheboygan, Wis., headquarters of Acuity Insurance, the pole spans 400 feet. That is seriously tall -- if you dropped a ball from the top of the pole, it would take five seconds for it to reach the ground (this according to the Internet's mathematicians, so don't hold me accountable).

Acuity hired Mortenson to build the pole, which is a "symbol of freedom and hope," said the firm's president and CEO Ben Salzmann. The pole was dedicated last month.

The pole consists of six steel tubes, and Mortenson officials say they utilized their expertiese from the firm's  renewable energy group for the project. Flagpoles are similar to wind turbine towers, apparently.

The flag is four stories tall, and two versions will be used: A 220-pound flag for normal conditions and a 350 pound flag for harsher weather.

The flagpole itself weighs about 420,000 pounds and is designed to withstand low temperatures up to 42 degrees below zero.

A video here describes the construction of the pole.