The Colosseum
With the fall of the Empire, the Colosseum was abandoned and became a quarry for building materials used to build many of the city's palazzos. This pillaging only stopped when a mid-18th century pope consecrated the site as a church. By then it was overgrown with exotic plants, seeds for which had been transported by the wild beasts that perished here, but the rare flora was yanked up after Italian unification in 1870.
This shot, taken further along the piazza del Colosseo, looks west towards the Vid dei Fori Imperiali.