Looking for a hotel with a difference? Try booking into a cave, a former jail, or maybe get cozy in a section of a drain pipe.

Editors at travel guidebook series Frommer's have come up with a list of the top 10 novelty hotels. This list was not endorsed by Reuters:

1. Pipe Dreams in Austria

What began as a pipe dream for architect Andreas Strauss became a concrete reality in 2005, when he built Das Park Hotel in 9-ton, cement drainage pipes in a public park on the banks of the Danube River at Ottensheim, upriver from the historic city of Linz.

The interiors are spartan chic with Internet access but toilets, food, and a bar are a walk away. Reserve online and receive an access code via email to open the door upon arrival.

The cost? Whatever you feel like paying.

2. Underwater Vacations in the Persian Gulf

If plans by submarine engineer Bruce Jones and His Highness the Crown Prince of Dubai go to schedule, 2009 will see the opening of the two largest undersea vacation destinations.

Hydropolis, a $580 million 220-suite hotel, will rest 66 feet below Persian Gulf waters, with 240 acres of submersed retail stores, restaurants, and guestrooms with sleeping-area walls and bathtubs made of clear glass. Double rooms are estimated to cost $1,500 a night.

3. Underwater in the South Pacific

Jones's Poseidon Undersea Resort is a $105 million hotel being built 40 feet below the coast of Fiji, with 270-degree floodlit views of active coral reefs. The resortwill also feature a wedding chapel and spa. They're taking reservations for 2009 soon. The cost? $15,000 a week per double.

4. Dive to your room in Florida

But if you can't wait another year, consider Jules' Undersea Lodge, 30 feet below the ocean surface in Key Largo, Florida. The lodge began in 1972 as a research lab and guests still have to dive to their rooms. The underwater habitat has two bedrooms and 42-inch windows to the abyss, teeming with nurse sharks, parrotfish, lobster, or barracuda.

5. In the Doghouse in Idaho

Dog Bark Park Inn is a 35 feet tall pine guesthouse shaped like a giant beagle. It has just one unit with a queen bed and kitchenette spreading out from the dog's rump through the belly. The dog's head houses a loft-style bedroom as well, with a sleeping alcove in the snout. Additional canine touches include dog-shaped cookies placed on the pillows.

6. Beam Me Up in Croatia

If you are looking for peace in Croatia, famous for its rugged, rocky coastline, consider renting a lighthouse. There are 11 of them available for rent along the Adriatic. All are active, with full-time keepers who can prepare meals for visitors.

7. Cave Hideaway in Turkey

If you're curious to know what it's like to live in a cave, head to Anatolian Houses. The hotel's 19 suites are constructed within five cave formations and have TVs, jacuzzis, and fireplace, and the property features a spa, indoor/outdoor swimming pool, Turkish bath, and wine fountain.

8. Wigwam Hotel in Holbrook, Arizona

Stay at a 1940s-era concrete teepee just off Route 66 at the Wigwam Motel, Holbrook, Arizona which is just one of several vintage motels offering teepee or wigwam-style rooms.

9. Underground motels in Australia

Try the Underground Motel in South Australia's Coober Pedy, an opal-mining town, or the White Cliffs Underground Motel in New South Wales where you also eat in an underground dining room.

10. Jailed in Tasmania, Australia

From the island-state of Tasmania, head farther offshore to Maria Island to stay in hostel-style accommodation in an old convict settlement in Darlington.