Last summer I sailed on the Celebrity Eclispe on a 14 day Baltic cruise. It was amazing. One of our ports was Tallin, Estonia.
Tallinn is a fascinating city. The old town is on a hill and is an easy walk from the cruise terminal. Most cruise lines offer busses also. Even though Tallinn was founded in 1248, the earliest human settlements are over 5,000 years old, which makes it one of the oldest capital cities of Northern Europe. Due to its strategic location on the Baltic Sea, the city became a major trade hub. It grew in importance as part of the Hanseatic League from the 14th to the 16th century.
The Old Town is filled with quaint, cobblestone streets. You enter the city through the old gates. It is a great city to wander and explore. And believe me, your legs will get a workout. Be sure to wear comfortable shoes!