One of the Gatun Locks. The double sets of doors prevent an accidental spill from Lake Gatun to the Caribbean Sea. A failure of the lock gates—for example, caused by a runaway ship hitting a gate—could unleash a flood on the lands downstream of the locks, as the lake above the locks (Gatun Lake or Miraflores Lake) drains through the lock system. Extra precaution against this is provided by doubling the gates at both ends of the upper chamber in each flight of locks; hence, there are four gates in each flight of locks that would have to fail to allow the higher level of water to pass downstream. The additional gates are 70 ft away from the operating gates.