The goal of this lecture is to give an account on spectral properties of tubular neighbourhoods of Riemannian manifolds. We focus on physical realisations when the base manifold is a curve in the three-dimensional Euclidean space, intensively studied during the last three decades because of physical motivations in quantum waveguides. These lecture notes consists of two parts: 1. General framework of arbitrary manifolds and dimensions: Light presentation and state of the art. 2. Special Euclidean tubes about curves: Detailed proofs and occasionally new results.