It's about one-and-one-tenth times as tall as Olympus Mons
In other words, the height of Olympus Mons is 0.910 times 30 kilometers.(a.k.a. Mount Olympus) (Mars)
The tallest mountain in the solar system, Olympus Mons rises to approximately 27 km. 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 two-and-a-half times as tall as Maxwell Montes
In other words, the height of Maxwell Montes is 0.370 times 30 kilometers.(Ishtar Terra, Venus)
Maxwell Montes rises to a total height of 11 km. 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 three times as tall as The Challenger Deep (Marianas Trench)
In other words, 30 kilometers is 2.75180 times the height of The Challenger Deep (Marianas Trench), and the height of The Challenger Deep (Marianas Trench) is 0.36340 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 10.902 km below sea level. There has been only one manned expedition to the bottom of Challenger Deep — a 1960 voyage that took 4 hours and 48 minutes to reach the bottom.
It's about one-third as long as The Panama Canal
In other words, the length of The Panama Canal is 2.90 times 30 kilometers.(Canal de Panamá) (Panama)
Connecting the Atlantic and Pacific Oceans across the Isthmus of Panama, the Canal measures 88 kilometers in length. Ships passing through the Canal are raised (and then lowered) 0.026 kilometers above sea level through the lock-and-dam system.
It's about three-and-a-half times as tall as a Mauna Loa
In other words, 30 kilometers is 3.2720 times the height of a Mauna Loa, and the height of a Mauna Loa is 0.30560 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 9.20 kilometers 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 three-and-a-half times as tall as Mount Everest
In other words, 30 kilometers is 3.390 times the height of Mount Everest, and the height of Mount Everest is 0.2950 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 is 8.850 kilometers above sea level at its summit. The plate tectonics of the Indian subcontinent continuously alter the mountain's peak â€” raising it by 0.00000400 kilometers and shifting it to the northeast by 0.00000450 kilometers each year.
It's about three-tenths as long as The English Channel
In other words, 30 kilometers is 0.280 times the length of The English Channel, and the length of The English Channel is 3.570 times that amount.(average width between Isle of Ushant and The Walde Lighthouse) (La Manche, Ärmelkanal, Mor Breizh, Mor Bretannek) (a.k.a. The Channel)
The English Channel measures between 180 km to 34 km, narrowing as it flows northeast. The world speed record for a Channel crossing by swimmer was set by Australian Trent Grimsey in 2012, with a time of 6 hours, 55 minutes.