  We consider Schr\"odinger operators in $L^2(\mathrm{R}^\nu),\, \nu=2,3$, with
the interaction in the form on an array of potential wells, each on them having
rotational symmetry, arranged along a curve $\Gamma$. We prove that if $\Gamma$
is a bend or deformation of a line, being straight outside a compact, and the
wells have the same arcwise distances, such an operator has a nonempty discrete
spectrum. It is also shown that if $\Gamma$ is a circle, the principal
eigenvalue is maximized by the arrangement in which the wells have the same
angular distances. Some conjectures and open problems are also mentioned.
