10 most difficult cities of Europe riddles

The convent was ruined in the 1755 Great Lisbon Earthquake, which destroyed the city, killed possibly 100.000 of its inhabitants and disrupted the colonial ambitions of Portugal. The church was left unrestored to remind the tragedy.

The Prague Metro is the rapid transit network of Prague, Czech Republic. Founded in 1974, the Prague Metro now comprises three lines, serving 61 stations, and consists of a transit network 65.2 kilometres (40.5 mi) long. Prague Metro system served 589.2 million passengers in 2012 (about 1.6 million daily), making it the fifth busiest metro system in Europe.

In 1624, during the reign of King Christian IV the city was destroyed by a fire. It was rebuilt and renamed Christiania in the king's honor. Following a spelling reform, it was known as Kristiania from 1877 to 1925, when its original name was restored.

This satellite photo is rotated so the North is at the bottom.

The Dubhlinn ("black pool") was a small lake used to moor ships and was connected to the River Liffey. This lake was covered during the early 18th century as the city grew.

Hamburg, with its 1.7 Million of inhabitants, is the second largest city after Berlin (3.4 Million). The largest urban area in Germany is the Rhine-Ruhr metropolitan region with 11M.

In 2012, seven of the fifteen tallest skyscrapers in Europe were located in Moscow. There are also several high-rise buildings under construction there.

The bear is the symbol of Madrid, just as in the case of Berlin. According to the popular story, the original name of the city was "Ursaria" ("land of bears" in Latin).

Copenhagen faces the Øresund to the east, the strait of water that separates Denmark from Sweden, and which connects the North Sea with the Baltic Sea. The Swedish towns of Malmö and Landskrona lie on the Swedish side of the sound directly across from Copenhagen.

The Dancing House is the nickname given to the Nationale-Nederlanden building in Prague, Czech Republic. It was designed by an architect Vlado Milunić in cooperation with Frank Gehry. There is a restaurant situated on the 7th floor of the building which boasts unique and breathtaking views of Prague Castle and Lesser Town.