Up on the cliff, in 1620, Champlain built the ancient castle of St. Louis, which stood on the verge of the rock, where now is the eastern end of the Dufferin Terrace, at an elevation of about one hundred and eighty feet above the river. This was of timber, afterwards replaced by a stone structure used for fort and prison, and burnt in the early part of the nineteenth century, the site being now an open square, with some relics, on the verge of the cliff. The great Quebec Citadel upon the summit of the promontory, three hundred and fifty feet above the river, is one of the most formidable of the former systems of stone fortifications. It covers forty acres, and has outlying walls, batteries and defensive works enclosing the entire ancient city, the circuit being nearly three miles. There are batteries guarding the water approach, gates on the landward side (some now dismantled), and four massive martello towers on the edge of the Plains of Abraham above the city, with long subterranean passages leading to them and other outlying works. The Quebec rock is a dark slate, with an almost perpendicular stratification, and shining quartz crystals found in it gave it the name of Cape Diamond. The portion of the works overlooking the St. Lawrence is called the Grand Battery, while the surmounting pinnacle of the Citadel, containing a huge Armstrong gun, is the King's Bastion. While Quebec's magnificent scenery and its tremendous rock-crowned fortress remain as they were during the great colonial wars, yet the military glory is gone. England long ago withdrew the regular garrison, and only a handful of Canadian militia now hold the place, and the guns are harmless from age and rust, only two or three smaller ones doing the present ceremonious duties. In fact the old rock is so given to sliding, that salutes are forbidden, excepting on rare occasions, lest the concussion may bring some of the fatal rock-slides down upon the people of the Lower Town. There is a little bronze gun preserved as a trophy in the centre of the Parade, which the British captured at Bunker Hill. Grand as this Citadel is, it no longer protects Quebec, for in fact the defense against an enemy is provided by the newer modern forts across the river behind Point Levis, which command the river approach and cost some $15,000,000 to construct.