Located in a former 19th century water purification plant, La Purificadora has become a favorite of travelers making the once dusty journey between the megalopolis that it is Mexico City and its country cousin Oaxaca. Designed by famed Mexican modernist architect Ricardo Legorreta, the hotel is a concert of colonial charm and the tongue-in-cheek tropical high design that made Legorreta an international star. Guests should remember to bring their best bathing suits: the inviting lap pool is transparent on two sides.