Canto IV

1. Italy was both the traditional destination of a Christian pilgrimage and the art lover's Grand Tour.  To the modern Haroldian sceptic, particularly a Briton who had been brought up in a protestant rational culture, a pilgrimage of Rome meant surveying a culture  riddled with a superstitious religion, which had been superseded by scientific and historical thought, and the ruins of past empires, which mocked the ambitions of rulers. 

2. The alienation and nihilism produced by secular, historical relativism could, however, be offset by the hole that Italy - the cradle of republicanism in the ancient world - would provide a rebirth of political liberty and enshrine it in the creation of a new nation-state.

3. For Republicans such as Byron and his friends, the ruins of ancient Rome were of a more than antiquarian interest. After the defeat of the French republic, young idealist turned to Italy(most of which was ruled by Austria) as well as Greece (part of the Ottoman Empire), and fixed on them their dreams of revolution against imperial, monarchical tyranny.  

4. Indeed, the aristocratic  Grand Tour tradition of which the poem is a product, had been an important contributory factor in engendering the concept of Italian nationalism. For it was classically educated tourists who had first conceptualised the peninsula as one entity, rather than a collection of city-states and regions. It then took the Napoleonic occupation to provoke a spirit of defensive patriotism amongst the inhabitants.

5. Byron's mention of the British 'betrayal of Genoa, of Italy, of France, and of the world': Byron was now taking the cudgels against his homeland and its Tory government in no uncertain manner. His poem would inculcate the opposite of British jingoism: cosmopolitanism. This was the Enlightenment virtue promulgated by travel. Italy had now become Byron's adopted country.

6. The Coliseum had been consecrated by the Church in order to commemorate the Christian martyrs who had died there, but Byron adapts the notion of pilgrimage to sacralise his own secular quest to fight back against oppression and injustice. Individual self-renewal is thus linked with the wished-for renewal of the independence of Italy. So the matter-of-fact reality of the tourist's visit to a famous place goes hand in hand with an almost supernatural apprehension of the Coliseum as a 'magic' spot in which the poet communes with the spirit of the dead.

137-138: Byron's Reflection on Colosseum