The Styrian Armoury (Landeszeughaus) is the world's largest historic armoury and attracts visitors from all over the world. It holds approximately 32,000 pieces of weaponry, tools, suits of armour for battle and ones for parades.
Between the 15th century and the 18th century, Styria was on the front line of almost continuous conflict with the Ottoman Empire and with rebels in Hungary. In order to defend itself it needed troops and these troops needed equipment. The Styrian Armoury results from the resulting need to store large quantities of armour and weapons, and was built from 1642 - 1645 by a Tyrolean architect called Antonio Solar.
After about 100 years in use, Austrian empress Maria Theresia wanted to close down the armoury, as part of her centralisation of the defence of Austria. Nevertheless Styria petitioned for the ongoing existence of the armoury for both practical and sentimental reasons. Their petition was accepted and the Armoury was left intact, but largely decommissioned.
References:The Walls of Constantinople are a series of defensive stone walls that have surrounded and protected the city of Constantinople (today Istanbul) since its founding as the new capital of the Roman Empire by Constantine the Great. With numerous additions and modifications during their history, they were the last great fortification system of antiquity, and one of the most complex and elaborate systems ever built. They were also the largest and strongest fortification in both the ancient and medieval world.
Initially built by Constantine the Great, the walls surrounded the new city on all sides, protecting it against attack from both sea and land. As the city grew, the famous double line of the Theodosian Walls was built in the 5th century. Although the other sections of the walls were less elaborate, they were, when well-manned, almost impregnable for any medieval besieger.