The Beni Enzar crossing at the northern edge of Melilla is the gateway to Morocco, and worth visiting for the sheer theatre of it even if you are not crossing. The border sits at the end of a busy commercial strip, and the contrast between the Spanish city behind you and the Moroccan town of Beni Ansar ahead is immediate and striking.
Day trips to Nador and the surrounding Moroccan coast are straightforward. Nador itself is not a major destination but offers a glimpse of ordinary Moroccan urban life, and the coast south of Nador has some good beaches. Bring your passport; EU citizens do not need a visa for Morocco.