With a population of nearly 45,000 people, Bornholm lies just to the east of Denmark. It features the largest medieval fortress in all of northern Europe at Hammershus, and enjoys a high temperature that averages only 67 degrees in its warmest months.
An island of 23,000 people that belongs to Sweden, Oland is connected to the mainland of the country by the Kalmar Strait and the Oland Bridge. It prominently features Hogsrum Hill and Lake Mockelmossen, as well as a habitat of rare and endangered species at the Stora Alvaret limestone pavement.
An Estonia island of close to 40,000 inhabitants, Saaremaa is located in the Moonsund archipelago. It was conquered by the Livonian Brothers of the Sword in 1227 and was the site of the important Battle of Saule in 1236. The island features mostly forested terrain, along with the 110-meter-deep Kaali meterorite crater.
The main island of the Aland archipelago in the Baltic, Aland is the smallest province in Finland and is inhabited by nearly 25,000 people. It commands the entrance to the port of Stockholm and features a rocky and thin soiled landmass, with many surrounding islands only short miles from any of the number of harbors on the island.
Rugen is Germany's largest island and home to over 75,000 Germans, making it the most populous island in the Baltic Sea. It was first populated about 6,000 years ago and is one of the most highly visited tourist spots in Germany. One of its main features is the chalk cliffs of the Jasmund National Park.
The largest Baltic Sea island and the fourth most populated, Gotland is a province and municipality of Sweden. It features the Gotska Sanden National Park, as well as a makeup of climbable sedimentary rocks, limestone and shale.
Estonia's second largest island, Hiiumaa is also a part of the Moonsund archipelago. It has been inhabited since the 4th century B.C. and was occupied during World War I by Imperial Germany and in World War II by both the Germans and the Soviets.