From the Super Mario Wiki
Victoria is a large city in the Mushroom World whose appearance is extremely similar to that of England, a place on Earth. This city is so called because, in fact, it resembles England in the Victorian period, named after Queen Victoria and corresponding to mid-to-late 19th century (which was the tenure of Victoria's reign, from 1837 to 1901). Victoria is also the name of one of the six states of Australia.
In The Super Mario Bros. Super Show! episode "The Adventures of Sherlock Mario", Mario, Luigi, Toad and Princess Toadstool venture to Victoria in search of the famous detective Herlock Solmes and wind-up saving Victoria from Professor Kooparity, Mouser, Tryclyde and Koopa Troopa, who attempted to flood all of Victoria.
Victoria is described by Mario as being the land of mystery, cloaks and daggers and screams in the night and is somewhat dark and gloomy in appearance at night, being surrounded by extremely thick fog. Victoria is evidentially somewhat advanced in terms of technology, as it was shown to have such things as telephone polls and a working sewer system. A horse pulled carriage appears to be the main mode of transportation in Victoria; notable landmarks in Victoria include the warped Tower of Victoria, Bonkers Street, which Herlock Solmes lives on and a clocktower resembling the famous Earth monument Big Ben.