Good idea to have an atlas at hand
Despite herself being in almost terminal decline, Spain acquired new African territory during The (European) Scramble for Africa in the late 19th century. In 1884 , Spain seized territory south of Morocco and north of Mauretania. A territory that became known as Spanish Morocco, and which today is known officially as Western Sahara. In 1976, twenty years after Morocco regained its national independent sovereignty, Spain withdrew from The Western Sahara in the face of Moroccan military incursion.
Today there is still an ongoing, but little reported. conflict in the region. It does not involve either Spain (as the ex colonial Power) or Mauretania (who gave up its own claim to the territory in 1979). Instead native West Saharans (The Sahrawi people) are fighting for their independence and deploying traditional guerrilla tactics, run by Polisario, from the part of Western Sahara in the east which they control (about 1/5th of all the territory) into the Moroccan controlled part. In order to keep the Polisaro guerrillas out, Morocco has built a sand wall, or berm, over 1,700 miles long. Additionally, the West Saharans are attempting to win the propaganda war by portraying Morocco to fellow 'Arab' countries as a neo colonial Power. Although the Sahwari people do indeed have Arab blood, they also have Berber and Black West African blood too. A number of African countries do in fact recognise the state of The Sahwari Arab Democratic Republic.
The position of The UN is that Western Sahara is a non-governmental territory administered by Morocco, as the successors to Spanish administrative control. The UN seeks, so far unsuccessfully, to hold a Referendum on the country's future.
In addition to the territory of Spanish Morocco, between 1912 and 1956, Spain held territory on the Moroccan side of The Straits of Gibraltar. This was as a result of European global politics. An attempt by France to keep Germany out of what it saw as 'its' sphere of influence in Morocco. In order to garner wider support France involved Spain and Britain. Britain neither gained, nor sought, Moroccan territory, but was happy that non-threatening Spain controlled the African mainland opposite Gibraltar.
Spain withdrew from this territory, known as The Spanish Protectorate of Morocco, on Morocco gaining full independence from France in 1956.
However, Spanish colonialism has not ended. The two port cities of Ceuta and Melilla, on the Moroccan Mediterranean coast, remain Spanish territory in 2021. Ceuta hit world media headlines last week when pictures of Moroccans seeking a better life in The EU, sailed, swam, even floated from Moroccan territory to Ceuta, only to be roughly handled by Spanish troops on arrival. Ceuta, and Melilla, are seen as easy gateways into Europe by people desperate for a better life. The pictures of Spanish troops reminded me of a photograph (reproduced in the Wikipedia article on The Spanish Protectorate of Morocco) which shows Spanish troops gleefully holding aloft the severed heads of captured Moroccans. The date? 1922.
Is it surprising that the wider world view of European colonialism is so tarnished?
Ceuta, a city with a small interior and a population of 85k, became Spanish in 1668 when, after the ending of the joint Portuguese/Spanish state, 1580-1640, Ceuta chose to be Spanish rather than Portuguese. The Portuguese themselves had first arrived in Ceuta in 1415 as part of The Reconquista (Reconquest of all of Portugal, and Spain, from Islamic rule). So in a sense it can be argued, as Spain does, that Ceuta has always been a European city in the Modern Age. This does not prevent, of course, Morocco arguing for its 'return', along with the other Spanish enclave of Melilla further down the coast towards Algeria, and 385 miles from Ceuta.
Melilla is a smaller piece of territory than Ceuta, only 4.7 square miles as against Ceuta's 7 square miles. Melilla has a population slightly larger than that of Ceuta, however, at 86.5k. Melilla was captured by Spain in the aftermath of victory over Islam in Spain itself in 1492, for it was in 1497 that the Spanish Government seized Melilla. Today the enclave is claimed to be an example of harmonious living between different peoples - Christian, Jew, Muslim, Hindu, and Buddhist.
NOTE. Despite disregarding Morocco's claims to its own two North African enclaves, Spain continues to demand the return of Gibraltar. Gibraltar became British at the end of The War of The Spanish Succession as negotiated at The Treaty of Utrecht, 1713. More importantly in our modern, post Woodrow Wilson world of national self determination, Gibraltar has twice voted in a Referendum, 1967 and 2002, to remain British. The vote being respectively 99.64% and 98.97% against union with Spain.