Building the HMS Dreadnought started in 1906 and finished in 1910. It was just over 20,000 tons and 526 feet in length. It had a crew of about 800.
By comparison, the largest cruise ship (as of Jan 2015) is the Royal Caribbean cruise ship Allure of the Seas. It is 225, 000 tons and has a length of 1,181 feet. It can accommodate 6, 306 people.