BEREZNIKI, Russia — Dmitry Rybolovlev, the Russian fertilizer tycoon who in February bought the most expensive apartment ever sold in New York City — the $88 million penthouse at 15 Central Park West — may have done a lot for real estate values there. But here in this old mining city in the Ural Mountains, where he made his fortune, not just property values, but properties too, have been plunging.

Sinkholes are common hazards in mining regions, plaguing areas where miners have burrowed into layers of soluble minerals and accidental floods have followed. But in Berezniki, as often happens in Russia, the problem has been magnified by past practices in which safety was not always the foremost concern.

In the West, mines are usually located far from populous areas, to reduce the risks of sinkholes to homes and other buildings. But Berezniki, a city of 154,000 that began as a labor camp, was built directly over the mine — a legacy of the Soviet policy of placing camps within marching distance of work areas.

And so Berezniki is afflicted by sinkholes, yawning chasms hundreds of feet deep that can open at a moment’s notice. So grave is the danger that the entire city is under 24-hour video surveillance. On a screen in the command center late last year, one such hole appeared as a small dark spot in a snowy field in the predawn hours, immediately threatening to suck in a building, a road and a gas station.