Building a large-scale military asset like a submarine can be difficult enough, but in today’s age of high-flying drones and spy satellites, keeping your military projects hidden from prying eyes can be just as huge an undertaking as the construction itself.

China, who has had their sights set on expanding and modernizing their military presence in Asia, particularly in the South China Sea, is well aware that American intelligence assets are trained on the ongoing construction of China’s second aircraft carrier (the first to be built entirely within China). Combine peeping satellites with Chinese military enthusiasts trying to sneak pictures of new projects as they develop, and a problem begins to take shape: How does China build new assets without giving the whole world a sneak peek into what they’re up to?

Bohai Shipbuilding Heavy Industrial Corporation, a Chinese construction firm, believes they have the answer. The new submarine plant they’re building in Huludao, Liaoning Province promises to offer China all the security they need while maintaining enough internal space to construct a whopping four attack submarines simultaneously—all while keeping prying eyes at bay.

By transitioning to an entirely indoor submarine construction process, China can keep potential opponents guessing about the shape of their hulls or the design of the propellers, each of which could be used to extrapolate an idea of what kind of sound signature a submarine may produce while functioning underwater.

This new facility could put China at an even pace with U.S. submarine manufacturing, whose facilities allow for six total submarines to be built simultaneously. China will not do away with their existing submarine construction sites, but rather will add this new facility to their existing infrastructure.

However, despite being able to keep pace with the United States in terms of construction numbers, China’s next-generation Type 095 attack subs are still woefully behind American submarines in terms of technological capabilities. It is expected to be quieter than previous Chinese iterations, as well as American Los Angeles-class and Russian Victor III- and Akula-class submarines—all of which saw construction in the 1980s. In effect, Chinese submarine technology is still near to 30 years behind that of the United States, meaning matching construction output may be a moot point.

As a frame of reference, modern American submarines like the Seawolf- or Virginia-class subs are said to be “quieter at 25 knots than the Los Angeles class at pierside.” Chinese subs, on the other hand, are only now reaching the level of silent capability Los Angeles-class subs achieved in the 1980s.

Of course, even submarines that aren’t equipped with the most advanced technology can still be quite difficult to track and engage, and increasing the number of submarines in China’s service will certainly make them more formidable. China already boasts the most technologically capable fleet of fighters in the region, as their F-22 copycat J-20 fighter could lay waste to the most advanced jets fielded by any of their local competitors.