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St. Peter's Basilica in Vatican City is the world headquarters of Roman Catholicism and one of the largest churches in the world. Founded by Constantine the Great in 324, it stands over the tomb of Saint Peter the Apostle.

A prominent sight between the Colosseum and Forum in Rome, the Arch of Constantine is an elegant triumphal arch erected in 315 to celebrate Emperor Constantine's victory over Maxentius at the Battle of Milvian Bridge.

Siena's cathedral is considered one of the great examples of Italian Gothic architecture, featuring exquisite inlaid marble and many art masterpieces.

A barrel-shaped church covered in marble, Santa Maria dei Miracoli is a fine example of Venetian Renaissance architecture and a favorite among Venetians for weddings. Inside, the coffered ceiling glistens with golden miniatures of prophets.

One of Europe's great icons, the Leaning Tower of Pisa is the bell tower of Pisa Cathedral. Although most famous for its astonishing lean, the tower is also notable for its magnificent Romanesque architecture.

Opened in 1935, the Griffith Observatory was founded by the land's former owner, who wanted to provide the public with direct access to science and the wonder of the stars.

Begun in 1914, the temple-like Lincoln Memorial occupies a prominent position at the west end of the Reflecting Pool in Washington, DC.