How are underground science facilities built underground?

Question

How are underground science facilities built underground?

Answer 1

Expensively.

Mainly its done two ways.  Either they build it like a regular building by excavating then backfilling over the building or they excavate only the nessacary space while they build.

The first way is less expensive as you just dig a big hole build what you want then fill the hole. (obviously this can only work if you are not going to deep.)

The second way is much more expensive, mainly because its more time consuming.  Deep buildings like bunkers or underground science facilities (by the way there is almost no point in building an undergroung science facility) are done this way.  Most of these buildings are made using concrete as it can be transported as a liquid then it hardens when placed.

The more interesting question then the one asked, is how do they build underwater?  The Answer :  Ninjas.