A brief walk downhill from Edinburgh Castle, this church - and its steeple in particular - is one of the most important architectural landmarks along the Royal Mile. Here is where Scotland's equal to Martin Luther, John Knox, preached his sermons on the Reformation. Also known as the High Kirk of St. Giles, the building combines a dark and brooding stone exterior (the result of a Victorian-era restoration) with surprisingly graceful buttresses. Only the tower represents the medieval era of the church. One of its outstanding features is the Thistle Chapel, housing beautiful stalls and notable heraldic stained-glass windows.