Spain, Catalunya, Barcelona, Antoni Gaudi's La Pedrera building, a section of chimney pots on the roof terrace.

Spain, Catalunya, Barcelona, Antoni Gaudi's La Pedrera building, a section of chimney pots on the roof terrace.

Spain, Catalunya, Barcelona, Antoni Gaudi's La Pedrera building, a section of chimney pots on the roof terrace.

Spain, Catalunya, Barcelona, La Pedrera by Antoni Gaudi, full view of the building's facade.

Spain, Catalunya, Barcelona, Antoni Gaudi's La Pedrera building, a section of chimney pots on the roof terrace.

Spain, Catalunya, Barcelona, distant view of La Sagrada Familia from the rooftop of La Pedrera .

Spain, Catalunya, Barcelona, La Pedrera by Antoni Gaudi, a section of the building's facade.

Spain, Catalunya, Barcelona, Parc Guell by Antoni Gaudi, ceiling Mosaic in the Hypostyle Room.

Spain, Catalunya, Barcelona, Parc Guell by Antoni Gaudi, one of the tiled mosaic benches on Banc de Trencadis.

Portugal, Lisbon, Belem Tower, 16th-century fortification that served as a point of embarkation and disembarkation for Portuguese explorers and as a ceremonial gateway to Lisbon, the tower symbolizes...

Portugal, Lisbon, Belem Tower, 16th-century fortification that served as a point of embarkation and disembarkation for Portuguese explorers and as a ceremonial gateway to Lisbon, the tower symbolizes...

Portugal, Lisbon, Belem Tower, 16th-century fortification that served as a point of embarkation and disembarkation for Portuguese explorers and as a ceremonial gateway to Lisbon, the tower symbolizes...

Portugal, Lisbon, Belem Tower, 16th-century fortification that served as a point of embarkation and disembarkation for Portuguese explorers and as a ceremonial gateway to Lisbon, the tower symbolizes...

Spain, Castile, Segovia, Puerta de San Andrés or St Andrew's Gate, part of the city's medieval defensive fortifications.

Fortification built on the end of Hurst Spit at the narrowest point of the Solent, opposite the Isle of Wight guarding the approaches to Southampton Port and Portsmouth harbour. First fort completed i...

Qatar, General, Aerial view of Zubara fort with the desert beyond.

Northern Ireland, County Derry, The Guild Hall, view from the city's 17th century walls with a cannon in the foreground.

Northern Ireland, County Derry, The Guild Hall, view from the city's 17th century walls with a cannon in the foreground.

Northern Ireland, County Derry, The Guild Hall, view from the city's 17th century walls with a row of cannons in the foreground.

Northern Ireland, County Derry, The Guild Hall, view from the city's 17th century walls with a cannon in the foreground.

Italy, Valle d'Aosta, castle towers, Fenis Castle.