The most outlandish synonym I have found is Brobdingnagian (with capital letter), with the meaning "marked by tremendous size". It refers to Brobdingnag, a fictional country in Jonathan Swift's classic novel Gulliver's Travels (1726). It is found here on the Oxford Dictionary site, and here on the Merriam-Webster Dictionary site.
Other words are lofty (rising to a great height, very tall and impressive), altitudinous (extending to a great distance upward), statuesque (tall and beautiful, of a woman), rangy (tall and thin, of a person), etc. All these words can be looked up on oxforddictionaries.com or merriam-webster.com for more elaborate descriptions and example sentences (except altitudinous, which is not found on the Oxford Dictionary site).