A magnificent part of California's natural history since its discovery in 1885, Mercer Caverns is home to a wealthy variety of natural cave formations. Visitors are invited to take a tour of the caverns and view a variety of stalactites, stalagmites, draperies, columns, flowstone, helictites, and soda straws. Gaze upon delicate aragonite crystal formations at one of the cavern's deepest points, for which Mercer Caverns won a Grand Prize at the 1900 Paris World Exposition.

Founded by governor Sir Henry Conway Belfield in 1917, this Gothic-style cathedral is one of the most important buildings of the Anglican Church of Kenya, and a prominent landmark of the British-Kenyan relations stemming from the 19th century.

Portland is home to the nation's largest wooded urban park—Forest Park. A short hike in, and you'll find it hard to believe that civilization is just steps away. With 70 miles of trails winding through the forest and offering views of the Willamette River, you'll often have nature all to yourself. However, you're also likely to run into locals jogging or walking their dogs—expect to be greeted with a friendly "hello." If you have the time, hike up to Pittock Mansion, a stunning French Renaissance-style château that once belonged to Henry Pittock, a prominent publisher and businessman. Today, the mansion serves as a historic house museum open to visitors, offering panoramic views of the city. Another popular destination within Forest Park is the so-called "Witch's Castle"—the moss-covered ruins of an abandoned stone house. Despite its eerie name, there’s no record of witchcraft here. However, legend has it that its original inhabitant was the first person in Oregon to be sentenced to execution for murder in 1859.