Changjon has had a number of improvements since 2005, including a new golf course, and a renovated harbor. It's also home to a naval base. Of course, Kumgang is nearby the very popular Mount Kumgang park.
The airbase was built between 2010 and October 2012. It has a 3,275 foot (1 km) long single runway and basic support facilities. It replaces the much smaller grass airstrip that once served the Kumgang area.
Here are the exact coordinates: 38°42'5"N 127°59'45"E (link opens Google Maps).
(Click image for larger view)
The facility has several aircraft dispersal pens, bunkers for either storage or maintenance, and 3 small fuel tanks. It will likely be used for civilian purposes, but as it stands, it can be considered primarily a military asset given its structure.
Despite being fairly new, and the levee built to divert the nearby river (North Korea has built many runways very close to rivers, which doesn't seem prudent), the place seems somewhat deserted and has been flooded at least once.
Also, between 2007 and 2012, the surrounding area saw some upgrades too. A new communications tower was built as well has new housing.
There are no defensive artillery emplacements (that I can find) which typically guard airbases of this size, but there are a few small military units up and down the valley. The town of Kumgang itself, though, is protected by 3 anti-aircraft artillery emplacements which contain a combined 18 guns.
When it comes to completing projects, North Korea can accomplish seeming wonders in a short time (except the Ryugyong Hotel, and the fact that most things aren't built very sturdy), but when it comes to making good use of them, things tend to take a while.
The newest images freely available date to October 2013, but given that so much effort is being placed on Pyongyang and Wonson, I don't think the Kumgang area will see much more activity for a while.