Seeing an exhibition there is extremely pleasant. ...

Seeing an exhibition there is extremely pleasant. Starting with the building, an old water tank, which in itself is worth the visit.
Continuing with the exhibitions that usually have, usually photographic, that are usually exposed in an existing composition.
Following its tracks where you can walk or run, extremely nice especially in spring.
And finishing because all this is free, and without crowds, it makes this one of my favorite places in Madrid.