It's about one-and-one-fourth times as deep as The Challenger Deep (Marianas Trench)
In other words, 686 chains is 1.2658 times the depth of The Challenger Deep (Marianas Trench), and the depth of The Challenger Deep (Marianas Trench) is 0.79001 times that amount.(near Marianas Islands, a.k.a. Ladrones Islands, northwestern Pacific Ocean) (depth below sea level)
The Challenger Deep, at the southern end of the Marianas Trench, reaches a depth of 541.940 chains below sea level. The first manned expedition to the bottom of Challenger Deep took 4 hours and 48 minutes in 1960. This was the only manned descent to the floor of the Trench until 2012, when director James Cameron made the trip; several other descents have been made since then.
It's about one-and-three-tenths times as tall as Maxwell Montes
In other words, 686 chains is 1.3 times the height of Maxwell Montes, and the height of Maxwell Montes is 0.77 times that amount.(Ishtar Terra, Venus)
Maxwell Montes rises to a total height of 550 chains. Since Venus does not seem to have the kind of tectonic activity which gives rise to mountains on Earth, the origin of the Venusian mountain remains the subject of some dispute.
It's about one-and-a-half times as tall as a Mauna Loa
In other words, 686 chains is 1.505 times the height of a Mauna Loa, and the height of a Mauna Loa is 0.6645 times that amount.(Hawaii) (Hawaiian island volcano) (total height from seafloor)
Mauna Loa, one of the five volcanoes which forms the island of Hawaii and the tallest mountain in total height in the world, rises to 457.30 chains above the seafloor. The peak of Loa is home to the approximately 6,000 sq. m (0.6 ha) Lake Waiau, one of the highest altitude lakes in the United States outside of Colorado.
It's about one-and-three-fifths times as tall as Mount Everest
In other words, 686 chains is 1.55954 times the height of Mount Everest, and the height of Mount Everest is 0.641215 times that amount.(a.k.a. Mount Chomolungma, a.k.a. Sagarmatha, a.k.a. Mount Qomolangma, a.k.a. सगरमाथा, a.k.a. Chajamlungma, a.k.a. ཇོ་མོ་གླང་མ, a.k.a. 珠穆朗玛峰, a.k.a. Zhūmùlǎngmǎ Fēng) (Sagarmatha Zone, Nepal and Tibet, China) (to summit, excluding snow depth)
Mount Everest rises 439.8740 chains above sea level at its summit. The plate tectonics of the Indian subcontinent continuously alter the mountain's peak â€” raising it by 0.000198839 chains and shifting it to the northeast by 0.000223694 chains each year.
It's about half as tall as Olympus Mons
In other words, 686 chains is 0.51 times the height of Olympus Mons, and the height of Olympus Mons is 2 times that amount.(a.k.a. Mount Olympus) (Mars)
The tallest mountain in the solar system, Olympus Mons rises to approximately 1,300 chains. The mountain has been known to astronomers since the nineteenth century because it is tall enough to rise above Mars' frequent dust storms.
It's about twice as tall as Aconcagua
In other words, 686 chains is 1.9822 times the height of Aconcagua, and the height of Aconcagua is 0.50449 times that amount.(a.k.a. Cerro Aconcagua) (Mendoza, Argentina)
Aconcagua measures 346.07 chains height at its peak. Although there is no definitive evidence that members of the indigenous Inca civilization ever reached the peak the mountain, numerous archeological sites have been found on the slopes of the mountain, including a naturally-embalmed Incan mummy was discovered on a 258.490 chains high ridge.
It's about two times as long as Calangute Beach
In other words, 686 chains is 2 times the length of Calangute Beach, and the length of Calangute Beach is 0.5 times that amount.(Goa, India) (approximate)
One of the most popular tourist destinations in Goa, Calangute Beach, the "Queen of Beaches," stretches about 7 km in length.