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
Old Soviet-era military building at Paldiski, on the Baltic Sea coast
https://en.wikipedia.org/wiki/Paldiski
Ämari Pilots’ Cemetery
A Soviet Air Force cemetery, with pilots' graves using aircraft tails as headstones http://www.atlasobscura.com/places/amari-pilots-cemetery
Butterfly near 59 Degrees North, 24 Degrees East
St. Catherine's Church, Muhu Island
https://en.wikipedia.org/wiki/Muhu_St._Catherine%27s_Church
Old barn, Saaremaa Island
https://en.wikipedia.org/wiki/Saaremaa
Angla Windmills, Saaremaa Island
https://en.wikipedia.org/wiki/Saaremaa
Kaali Meteorite Crater, Saaremaa Island
Created about 7,600 years ago, when people were already living in the area http://www.amusingplanet.com/2014/03/kaali-meteorite-crater.html
Kuressaare Castle, Saaremaa Island
https://en.wikipedia.org/wiki/Kuressaare_Castle
'The Leaning House of Tartu'
https://www.visitestonia.com/en/the-leaning-house-of-tartu