The Grand Tour was a period of foreign travel commonly undertaken by gentlemen to finish off their education. The Grand Tour was only undertaken by the very rich, mainly the sons of the aristocracy.
It was popular from the mid 17th century until the end of the 18th century when the outbreak of the Napoleonic Wars stopped most foreign travel. It saw a revival in the early 19th century after peace was restored in Europe.
Strangely, I was just talking about this the other day - saying how sad it was that Italy's in such a mess at the moment, and what a lovely country it is, and how the old Grand Tour used to centre on Italy.