- Waterproof - Tear-Resistant - Topographic Map As a demonstration of the Roman Empire's power and strength, Emperor Hadrian conceived the idea to build a wall to deter attacks on his Roman territory Britannia. At the time -- and even today -- building a 73-mile (118-kilometer) long wall, standing 5 meters (16 feet) high and 3 meters (10 feet) wide was an exceptional undertaking. In a.d. 122, approximately 15,000 soldiers were enlisted...