Building underground has got both it's positives and it's negatives. However there are also certain structural requirements for underground building.
Below ground structures are actually far more suited to living in than we may believe. In fact they are more suited in some ways than above ground structures are. For example, they are very thermally efficient and so don't need as much insulation, the same is true for noise insulation too. As such, living underground generally removes the need for heating in the Winter. Also, because they are submerged below ground, out of direct sunlight, underground living can be cooler in the Summer too. Therefore, temperatures inside an underground structure are often very consistent, especially considering that they are not vulnerable to changes in the weather. Living underground can result energy costs which are only 20% of an equivalent normal house. The saving can then be used to invest in technology such as solar panels, which can potentially reduce costs to nothing.
There are more pros to living underground though. The use of lots of glass can actually result in more light reaching some areas than in conventional houses, making them feel spacious. Condensation is never a problem for underground buildings and due to the necessity of ventilation systems, air is capable of being consistently clean and clear. Fire risks are also very low in underground buildings and systems can be put in place to protect against them as with any building. In fact, because of the low fire risks, insurances are often cheaper than for normal houses.
The actual structure of underground buildings have to be built slightly differently. Walls must be thicker and stronger to support the pressure of the earth pushing on them. They must be able to withstand the subtle shifts in the earth and cannot be susceptible to breakages due to vibrations, from other construction or roads for example. The materials used should also be able to resist damp and mould, which threaten the integrity of structures and can result in collapse.
However, if built properly, the buildings require minimal upkeep. They are not at threat from weathering or vandalism and are held together by the earth itself. They are also very secure due to being buried, they cannot be broken into as easily for example. On that subject, being buried underground means that they have minimal, if not no, visual impact on the surface. This leaves more space for open, green spaces at ground level, or more housing if needed. In this project though, the site is so natural that underground living would be perfectly suited to preserving it. The same can be said to be true for other such sites too.