a - A famous battle between King Gustavus Adolphus of Sweden and Count Tilly occured here:
2 Battle of Breitenfeld 1631, near Leipzig.
b - The Alhambra can be found here:
15 A palace for the Moorish rulers in Granada
c - A national hero in this country:
13 Skanderbeg (Dragon of Albania), fended off Ottoman attacks in the middle of the 15th century
d - The oldest university in Europe is located here:
1 University of Bologna
e - Napoleon was born here:
4 Corsica
f - This man was born here:
6 Franz Kafka, born in Prague
g - The first naval battle in WWI occured here:
10 Battle of Heligoland Bight in 1914
h - The oldest functioning salt mine in Europe can be found here:
14 Near Krakow
i - A strange looking sea fort:
9 Maunsell Forts. Found this by accident when looking for questions.

j - The last country in Europe with women's suffrage:
7 Liechtenstein
k - Europe's worst maritime disaster (in terms of casualties) in the 1990's happened here:
11 MS Estonia in 1994
l - This place marks the most northern border of the Roman Empire:
5 Hadrians wall (more correct: Antonine Wall)
m - The tallest construction that has ever been moved to another position is found here:
12 The Troll A platform in the North Sea
n - The Varangian Guard served in this city:
8 Vikings serving the Byzantine Emperor in Constantinople/Miklagard
o - Another famous battle:
3 Battle of Tours/Poitiers. Charles Martel stopped the Muslims.