The Royal Mile is the name given to a succession of streets forming the main thoroughfare of the Old Town of the city of Edinburgh in Scotland. The name was first used in W M Gilbert's Edinburgh in the Nineteenth Century, and was further popularised as the title of a guidebook, published in 1920. The thoroughfare, as the name suggests, is approximately one Scots mile long and runs downhill between two significant locations in the history of Scotland, namely Edinburgh Castle and Holyrood Palace. The streets which make up the Royal Mile are Castlehill, the Lawnmarket, the High Street, the Canongate and Abbey Strand. The Royal Mile is the busiest tourist street in the Old Town, rivalled only by Princes Street in the New Town.