Cruise ships are large passenger ships used mainly for vacationing. Unlike ocean liners, which are used for transport, cruise ships typically embark on round-trip voyages to various ports-of-call, where passengers may go on tours known as "shore excursions". On "cruises to nowhere" or "nowhere voyages", cruise ships make two- to three-night round trips without visiting any ports of call. Modern cruise ships tend to have less hull strength, speed, and agility compared to ocean liners. However, they have added amenities to cater to water tourists, with recent vessels being described as "balcony-laden floating condominiums". As of December 2018, there were 314 cruise ships operating worldwide, with a combined capacity of 537,000 passengers. Cruising has become a major part of the tourism industry, with an estimated market of $29.4 billion per year, and over 19 million passengers carried worldwide annually . The industry's rapid growth saw nine or more newly built ships catering to a North American clientele added every year since 2001, as well as others servicing European clientele until the COVID-19 pandemic in 2020 saw the entire industry all but shut down. As of 2022, the world's largest passenger ship is Royal Caribbean's . History Origins Italy, a traditional focus of the Grand Tour, offered an early cruise experience on the Francesco I, flying the flag of the Kingdom of the Two Sicilies. Built in 1831, the Francesco I sailed from Naples in early June 1833, preceded by an advertising campaign. Nobles, authorities, and royal princes from all over Europe boarded the cruise ship, which sailed in just over three months to Taormina, Catania, Syracuse, Malta, Corfu, Patras, Delphi, Zante, Athens, Smyrna and Constantinople, providing passengers with excursions and guided tours, dancing, card tables on the deck and parties on board. However, it was restricted to the aristocracy of Europe and was not a commercial endeavour. P&O first introduced passenger-cruising services in 1844, advertising sea tours to destinations such as Gibraltar, Malta and Athens, sailing from Southampton. The forerunner of modern cruise holidays, these voyages were the first of their kind. P&O Cruises is the world's oldest cruise line. The company later introduced round trips to destinations such as Alexandria and Constantinople. It underwent a period of rapid expansion in the latter half of the 19th century, commissioning larger and more luxurious ships to serve the steadily expanding market. Notable ships of the era include the SS Ravenna built