With more than 1,400 Greek Isles dotting the Aegean and Ionian Seas, how do cruise lines select just a few to call upon? Just over 220 of the islands are inhabited, which narrows the choices. And, three of those islands – Santorini, Mykonos and Rhodes – have the distinction of being the most visited.

Make sure you’re out on deck during your ship’s approach to Santorini. You’ll sail right into the caldera of an ancient volcano, now filled with deep blue water. The capital city of Fira sits atop dramatic cliffs that rise 1,500 feet above the water. A must-see site on Santorini is the archeological ruins of Akrotiri, preserved under a layer of volcanic ash more than 3,600 years ago. An excavation of the Minoan-era site has been in progress since 1967.

Mykonos is an island with a relaxed, festive atmosphere. While there are no ancient ruins here, there are beautiful beaches, charming whitewashed buildings and cobblestone streets lined with shops, cafes and clubs. Many cruise lines offer excursions to the nearby island of Delos, an important archeological and historical site. Landmarks among the ruins there include the Terrace of the Lions, the Temple of Isis and the House of the Dolphins.

At the island of Rhodes, cruise ships dock just a short walk away from the medieval Old Town. There are hundreds of restaurants and shops to browse for jewelry, leather goods, linens and more. The Colossus of Rhodes, the bronze statue said to be one of the seven wonders of the ancient world, no longer guards the harbor but there are many other wonderful sights, such as the Palace of the Grand Master. In addition, there is a spectacular acropolis at Lindos, a 45-minute drive from the city of Rhodes.

There are some must-have items for a cruise of the Greek Isles. Pack some good shoes for walking on cobblestone streets and the uneven ground of archeological sites. Bring cool clothing to wear in the heat of the day. Many of the islands are nearly treeless, so pack a broad-brimmed hat, sunscreen and sunglasses.

Some of the best times to visit the Greek Isles are late spring and early autumn, when temperatures are cooler than they are at the height of summer. Still, almost any time of the year is beautiful in the Greek Isles, and a wide variety of cruise ships sail there.