Bored of beige rugs and hotel rooms that look the same no matter where you are in the world? Then maybe it's time to consider unique and affordable vacation rentals. Whether you're looking to sleep in a tree or castle, here are six rentals around the world sure to capture your imagination. Best of all, these places are within reach, with rates lower than $100 per night per person.

"Onion House" in Hawaii

The ultimate in island indoor-outdoor living, the well-known Onion House on the Kona Coast of Hawaii's Big Island offers a totally unique taste of tropical paradise. The translucent arching domes that give this house its name inspired one person to declare it "The Sydney Opera House meets Stonehenge." Stained glass, swimming pools, fish ponds, and gardens add to the enchantment. The house sleeps six; with six people, each guest pays $58 to $75 per night, depending on the season.

Castle in France

If your aspirations are a little grander, perhaps a castle in France is more your speed. The 900-year-old Chateau d'Alogny has been spruced up since its earliest days, and now boasts a modern kitchen, satellite TV, and under-floor central heating. With five bedrooms and four bathrooms, the castle sleeps 10 people comfortably. Located just south of the Loire Valley between the cities of Tours and Poitiers, there's plenty to do nearby. Split between 10 people staying for a week, the nightly rate comes out to $44 to $75 per person, depending on the season.

Yurt in Oregon

Round, canvas, fancier than a tent, but more rustic than a house. It's a yurt!

Yurts in Oregon State Parks sleep five people, and have heat and electricity plus an outdoor fire pit and picnic table. As with camping though, you'll need to bring your own bedding and dishes. More than a dozen coastal and four inland parks rent yurts year-round, with rates between $27 and $30 a night. You can find yurts to rent in other places — including California, Hawaii, and Costa Rica, among others— as well.

Tree House in Costa Rica

Look forward to an elevated experience at the Playa Selva Tree House in Mal Pais, Costa Rica. And it's not your typical tree house, either. This one sleeps three people, and has a full bath with hot water, a kitchenette, and a balcony. Perched in a Banyan tree, the tree house is the perfect place to catch a glimpse of howler monkeys, tropical birds, and other native wildlife. There's a swimming pool on the property, and the rental is a short walk from the beach. Rates vary between $50 and $65 a night, based on the season.

Farmhouse in Italy

For under $100 a night, you can drink in the Tuscan sun from your very own farmhouse. Close to the towns of San Gimignano and Volterra, Casa Quintino is about an hour from Florence, Pisa, and Siena. The renovated farmhouse retains its old world charm while offering modern amenities such as Internet access and modern bathrooms. The property includes a ruined Benedictine chapel, oak forests teeming with wildlife (and truffles!), and a natural spring. Rates vary between $80 and $105 per night, depending on the season.

Fire Lookout in the West

Want to really get away from it all? Maybe a former fire lookout or ranger cabin, miles from the nearest electrical outlet, is just the thing. Western states including California, Idaho, Montana, and Oregon are dotted with former stations now offered as very basic accommodations. Amenities vary by location. For instance, at the Bear Basin Lookout and Cabin in California's Six Rivers National Forest, the fire lookout and cabin come with beds and foam pads, tables and chairs, and fantastic scenery. At the Castle Butte Lookout in Idaho, you get 360 degrees of views, plus beds and a stove. Rates start at about $30 per night.

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