Marseille is a beautiful city with a rich history and culture. Here's an ideal itinerary for 4 days in Marseille:

Day 1:

• Start your day with a visit to the iconic Notre-Dame de la Garde, a stunning basilica that offers panoramic views of the city.
• After that, head to the Old Port (Vieux-Port) and take a stroll along the waterfront. You can also take a boat tour of the harbor and see the city from a different perspective.
• For lunch, try some of the local specialties like bouillabaisse (a fish stew) or socca (a chickpea pancake).
• In the afternoon, visit the MuCEM (Museum of European and Mediterranean Civilizations) and learn about the history and culture of the region.
• End your day with a visit to the Palais Longchamp, a beautiful monument that houses a museum and a park.

Day 2:

• Start your day with a visit to the Calanques, a series of stunning rocky cliffs and coves that are perfect for hiking and swimming.
• After that, head to the Château d'If, a fortress that was made famous by Alexandre Dumas' novel "The Count of Monte Cristo".
• For lunch, try some of the local street food like panisse (a chickpea fritter) or a Marseille-style pizza.
• In the afternoon, visit the Musée des Beaux-Arts, which houses a collection of art from the 16th to the 19th century.
• End your day with a visit to the Cours Julien, a vibrant neighborhood that is known for its street art and trendy shops.

Day 3:

• Start your day with a visit to the Basilique Saint-Victor, a beautiful church that dates back to the 5th century.
• After that, head to the Jardin des Vestiges, an archaeological site that showcases the ancient history of Marseille.
• For lunch, try some of the local seafood like grilled sardines or octopus salad.
• In the afternoon, visit the Musée d'Histoire de Marseille, which tells the story of the city from its founding to the present day.
• End your day with a visit to the Parc Borély, a beautiful park that is perfect for a relaxing stroll.

Day 4:

• Start your day with a visit to the Cathédrale de la Major, a stunning cathedral that combines Romanesque and Byzantine architecture.
• After that, head to the Fort Saint-Nicolas, a fortress that offers great views of the city and the sea.
• For lunch, try some of the local street food like a pan bagnat (a sandwich with tuna, vegetables, and olive oil) or a fougasse (a type of bread).
• In the afternoon, visit the Musée Regards de Provence, which showcases the art and culture of the Provence region.
• End your day with a visit to the Plage des Catalans, a beautiful beach that is perfect for swimming and sunbathing.

I hope this itinerary helps you plan your trip to Marseille!