  The relativistic flux tube model is an effective description of confined
quarks and gluons in which the confining interaction is carried by the flux
tube, a Nambu-Goto string. We first show that the relativistic flux tube model
can be applied to glueballs seen as bound states of transverse constituent
gluons. After a comparison of that approach with usual spinless Salpeter
Hamiltonians, we compute glueball masses and decay widths. Comments about the
$\eta$-$\eta'$-pseudosclar glueball problem, the glueball--Pomeron conjecture,
and finite-temperature effects are finally given. We also point out the
existence of a duality between open- and closed-flux tube models of glueballs.
