During the Soviet era, the top floor of this hotel was off-limits...
This was the official 'Intourist' (Soviet travel agency) hotel for visiting foreigners.
...because it was a KGB listening post. The hotel rooms were all bugged
http://www.atlasobscura.com/places/kgb-museum
Tallinn Port
Alexander Nevsky Cathedral, Tallinn
https://en.wikipedia.org/wiki/Alexander_Nevsky_Cathedral,_Tallinn
Historic Old Town, Tallinn
http://whc.unesco.org/en/list/822 https://en.wikipedia.org/wiki/Tallinn