A mere 1.25 miles (2.01 km) off the coast of San Francisco, Alcatraz Island boasts a fascinating history that extends far beyond its stint as a federal penitentiary from 1934 to 1963; it is also the site of the West Coast's oldest operating lighthouse, the remains of a historic military fortress, and a bird sanctuary. Although within sight of the city, Alcatraz is isolated from the outside world, surrounded by the frigid waters of the bay, the perilous currents making escape virtually impossible. This very fact made Alcatraz an apt choice for a prison meant to house some of the country's most notorious criminals, including the likes of Al Capone, Robert Franklin Stroud and Alvin Karpis. The year 1969 marked the beginning of another intriguing chapter in the history of Alcatraz when a group of Native American activists occupied the island for 19 months, signs of which are still visible to this day. Amid this turbulent narrative thrives a vibrant habitat for native flora and fauna, creating a miniature world of startling contrasts where the haunting remains of the prison stand amid a striking landscape of rock pools, rugged coasts and lush flora. The isle is now a tourist attraction, one of San Francisco's most popular, with self-guided and guided tours that delve into the past of the island as a whole and the prison in particular.

The story of Anne Frank is one that is known the world over; an emblematic personal account of the Holocaust that is now preserved at the Anne Frank House. Spurred by the German occupation of the Netherlands, and the subsequent persecution of the Jewish community, Anne went into hiding with her family on July 6, 1942. Over the course of two years, Anne maintained a diary detailing life in the Annex, that was eventually published by her father. Although there aren't many memorabilia, films and other sources, including Anne's diary, present a vivid picture of what life was like during those times. The museum opened on May 3, 1960, and the enormous visitors' center was constructed in the 1980s.

A leafy enclave in Coyoacán preserves behind vivid blue walls the legacy of one of Mexico's most iconic artists, Frida Kahlo. Known as the iconic Casa Azul, or Blue House, the Museo Frida Kahlo was the birthplace of the enigmatic painter Frida Kahlo, who also occasionally lived here with her husband Diego Rivera. One of Mexico city's most recognized attractions, the house contains everything from her personal belongings such as jewelry, and unfinished canvases propped on easels, to her traditional tehuana dresses. The museum is lavishly divided into ten rooms, each a splendid glimpse into the artist's extraordinary work and life. Each room takes one on a riveting journey of Kahlo's life that she shared with her artist husband Diego Riviera, from rooms that once rung with animated soirées hosted for their artist friends, to rooms that still hold regional handicrafts that adorned their home. Other exhibits include paper maché skeletons of Judas and pre-Hispanic objects, as well as Kahlo's wheelchair, on display in the studio where she once regularly painted. The house museum spills into a sun-drenched courtyard lined with trees, burning bright with an inspiring legacy left behind by one of the country's brightest and most creative minds.

The controversial but decidedly beautiful sail-like roofs of Sydney's most recognizable icon glisten against the backdrop of Sydney Harbour. The Sydney Opera House was constructed over a fourteen-year period and caused an opera’s worth of drama that involved differences between the architect Jørn Utzon and the Australian government. The now world-renowned architectural wonder stands as an unmissable icon of Sydney's cultural landscape. It houses among other small venues, the Joan Sutherland Theatre, the Utzon Room and a grand Concert Hall. It also has an impressive yearly program of contemporary and classical performances, and is a striking cultural sanctuary to take in theater, opera and ballet. Riveting guided tours take visitors behind the scenes and into the establishment’s many interesting rooms.

One of the most prominent art museums in the world - Uffizi Gallery, is located in the Uffizi Complex that dates back to 1581. Much of the collection was bestowed upon the state of Tuscany by the Medici family in the 1700s to ensure that the work of some of Italy's greatest artists would remain where it belonged for the benefit of its people. The gallery consists of 40 rooms showcasing the work of some of the world's most renowned Renaissance masters, including Leonardo da Vinci, Michelangelo, Raphael and Caravaggio and also includes Botticelli's Birth of Venus and Primavera. Works of distinguished Flemish, Dutch and German painters are also on display here. The corridors and ceilings are anointed with splendid frescoes and lined with 16th-century Roman sculptures. Originally built to house legislative and administrative offices, the Uffizi Complex is a work of art in itself, designed by the noted architect, Giorgio Vasari.

This museum in Amsterdam has the world's largest collection of famous Dutch artist Vincent Van Gogh's works, from paintings to sketches and even letters. The museum chronicles the artist's career, from his years living in Nuenen, Netherlands beginning in 1880, up to his years in France and till his death in 1890. Some of Van Gogh's most famous works are on display in these galleries, including The Potato Eaters, Sunflowers and Bedroom in Arles. The museum also chronicles works by some of Van Gogh's artist friends and inspirations, including Toulouse-Lautrec and Paul Gauguin, with whom Van Gogh had a close friendship, and Jean-François Millet.

On New Zealand's North Island lie the Waitomo Glowworm caves, a natural phenomenon that brings to life the magic of nature. Home of the Arachnocampa luminosa or gloworm as it's commonly known, these underground grottoes are illuminated by the light of these minute creatures. The walls and ceiling of the limestone caves glow with iridescence, creating a microcosm of living stars. Boat tours depart every half hour and guides offer a whispered history of the caves and their geology as visitors gently drift down the Waitomo River.

An unfinished religious icon that is steeped in profound cultural value and features an incomparable aesthetic, the Basilica de la Sagrada Familia is an astounding marvel. Gaudí began working on this utterly surreal temple, now a renowned UNESCO World Heritage Site, in 1882. Originally intended to be a modest, neo-Gothic church, the Basilica de la Sagrada Familia has since become arguably the most iconic building in all of Barcelona. Gaudí broke away from the reigning neo-Gothic style in the late-19th and early-20th centuries, imbuing his architecture with symbolic meaning and pioneering the Catalan Modernism movement. Intricate details like palm-tree pillars whose bases take the shapes of turtles, eye-catching colors, Baroque-style influences, and materials ranging from mosaic tiles to an array of stones converge to create an absolute masterpiece.

Schönbrunn Palace in its present form is one of Vienna's most popular tourist attractions, hosting thousands of visitors a week. This Rococo Palace was finished in 1700 under Leopold I and is a smaller version of an imperial project first planned by Johann Fischer von Erlach. The palace was renovated and extended under Maria Theresia, and at that time had 2,000 rooms, a chapel and its own theater. Like all the imperial buildings associated with Maria Theresia, the Schönbrunn complex is today painted in yellow. Napoleon lived here from 1805 to 1809, and Emperor Francis Joseph I, who was born here in 1830, spent the last years of his life in the palace.

This extravagant ancient bath complex is an excellent example of Ancient Roman spa architecture dating back as far as 43CE. Built around three hot springs that steam and bubble at a constant 46 degrees centigrade (115 degrees fahrenheit), the baths offer insight into the daily life of the Romans. A Sacred Spring feeds the Great Bath and the complex opens out into a series of changing rooms and baths to either side of the central bath. As per tradition, there is also a cold plunge pool for bathers to cool off after a hot sauna. The complex also features a temple devoted to Sulis Minerva, the Celtic goddess of healing and fertility that the Romans worshipped as Minerva Medica. Exhibits and Roman artifacts include a famous stone relief of the Gorgon's Head, mosaics, stone coffins, and a gilded head from a statue of Sulis Minerva.

This masterpiece of Moorish architecture is one of the most inspiring set of buildings in Spain and is consequently the country's most visited historic site. A visual feast of intricate details, splendid courtyards and opulent ornaments, Alhambra is a place where artistic flourishes abound amid stately facades. The complex is made up of three parts: a fortress (Alcazaba), royal palaces (Alhambra) and a summer palace with luxuriant gardens (Generalife). The buildings date mainly from the 13th and 14th Centuries, after the Arabic Nasrid prince, Ibn al-Ahmar, made Granada an independent Moorish state. Each succeeding Nasrid ruler continued to beautify the royal palaces, combining wood, plaster, marble, brick and ceramic tiles with Arabic calligraphy, the scene enriched by tranquil waterways and babbling fountains amid landscaped gardens alive with birdsong.

No other natural phenomenon in Ireland competes with the Giant's Causeway when it comes to physical presence. The causeway consists of 40,000 hexagonal stone basalt columns spread out along the seafront in a bizarre honeycomb marine highway. Created by volcanic lava eons ago, the legend goes that a giant began building a shortcut to Scotland and halfway through, ran out of stone. This UNESCO Heritage site is home to unique sights like the thrilling Shepherd's Steps; the stone Wishing Chair, a natural throne built from columns; the legendary Giant's Boot and of course, the sweeping Grand Causeway set against the dramatic backdrop of the sea-lashed Irish coast.