The Mammoth Cave in Kentucky, USA, is the largest known underground cave system in the world, with over 400 miles of passages mapped and explored. It is a popular destination for cave enthusiasts and tourists due to its vast size and unique geological formations.
The largest discovered underground labyrinth is Carlsbad Caverns in Carlsbad, New Mexico. It has many tunnels and caves that continue for miles.Carlsbad, California is the site of the largest underground labyrinth found in the US. The total length of the labyrinth is still unknown, but the explored part of the main cavern is more than 30 miles long.
Mammoth CaveADDED: Depends on how to defines largest; but Mammoth - Flint Ridge Caves system has certainly world's longest knowntotal of surveyed passage length, I believe now >400 miles.
The largest mountain in our solar system is Olympus Mons on Mars.
At 26 kilometers high, Olympus Mons on Mars is the largest volcano in the solar system. It's also the largest mountain in the solar system.
The largest mountain system in North America is the Rocky Mountains, which extend from Colorado all the way to Alaska, which is about 2500 to 4000 miles. The second largest is The Appalachian Mountains.
It is the largest planet in the Solar System, having a diameter of 88846 miles at its equator.
The London Underground is Europe's largest metro subway system and is the world's oldest underground system (it was inaugurated in 1863). It covers 253 miles of track and transports 976 million people yearly. The Underground is also connected to a variety of rail services to London's surrounding areas (including the Eurostar to Paris). Among these services is the Docklands Light Railway (DLR), a popular driverless light rail extension, which offers many scenic views of the Thames river and surrounding areas Source: http://www.virgin-vacations.com/11-top-underground-transit-systems-in-the-world.aspx
Jupiter is the largest with the largest diameter.
Mammoth Cave with over 390 miles of passageways is the largest known cave complex.
Saturn has a radius of 36,184 miles (58,232 kilometers). This makes Saturn the second largest planet in the Solar System, after Jupiter.
Mammoth Cave has about 390 miles, or about 625 kilometers, of underground passages already mapped, far exceeding any other cave system in the world. And that's just what's been mapped -- spelunkers admit they are nowhere near exploring every last tunnel.