Over time the people were unified and divided depending on the ruling group. The Romans helped introduce the Spanish language, which is based on Latin, they also left behind some impressive architecture, some genetic diversity, and Christianity, all of which survive to this day.
Despite the unity, over time much of Spain was divided as the Basques maintained their language and culture to a great degree. The Catalans also diverged with a unique culture that differed from that of much of Spain. Many Jews also arrived to the region as did the Muslim Moors. All of these people influenced the culture, but the Moors had arguably the greatest impact as they introduced new foods and architecture. These both influenced modern Spain and Spanish cuisine is very unique as it mixes flavors from the Middle East and Europe.
Spanish culture has changed numerous times since the Moors, partially due to the country's regular division and unification. The lands have moved from world power to being taken over by foreign powers. Today Spanish culture can be defined in one way, a way that incorporates Moorish, Jewish, and local foods, music that has been inspired by Africa, Europe, and the Roma, and a lifestyle that mixes historic farms with urban centers. However, more than this, Spanish culture is defined by the many sub-cultures, including the Catalans in Barcelona, the Basques in the country's north, the Roma found throughout the country, and the many regional Spanish sub-cultures.