The Tower of London with the office blocks of London's financial district, the City, behind. The tower was begun by William the Conqueror in 1078 and added to over the centuries. The Tower today is principally a tourist attraction. Besides the buildings themselves, the British Crown Jewels, a fine armour collection from the Royal Armouries, and a remnant of the wall of the Roman fortress are on display. The tower is manned by the Yeomen Warders (known as Beefeaters), who act as tour guides, provide discreet security, and are something of a tourist attraction. Every evening, the warders participate in the Ceremony of the Keys, as the Tower is secured for the night.