  Human towers or castells are human structures played in festivals mainly in
Catalonia. These unique cultural and traditional displays have become very
popular in the last years, but they date from the XVIII century. On 2010 they
became part of the Unesco Representative List of the Intangible Cultural
Heritage of Humanity.
  Safety is very important in the performance of castells. To this end, it is
crucial to understand the mechanisms that allow a castell to be built and, more
importantly, the factors that may cause its collapse. This work is focused on
the mechanical aspects that make a pilar (the simplest structure in the
castells) to stand. We suggest three different but complementary approaches for
the running stage of a pilar (stage where it has been built and has not yet
collapsed): the $N$-link pendulum as a first dynamical model, the response of
the castellers as a control problem, and a static analysis to capture the
feasibility of a given configuration. We include some preliminary simulations
to better understand the previous approaches, which seem to match with
qualitative perceptions that castellers have of a castell. Possible future
developments are also discussed. To our knowledge, this work represents the
first one to study the castells from a mechanical point of view.
