The rough Bergomi (rBergomi) model, introduced recently in [4], is a promising rough volatility model in quantitative finance. It is a parsimonious model depending on only three parameters, and yet exhibits remarkable fit to empirical implied volatility surfaces. In the absence of analytical European option pricing methods for the model, and due to the non-Markovian nature of the fractional driver, the prevalent option is to use the Monte Carlo (MC) simulation for pricing. Despite recent advances in the MC method in this context, pricing under the rBergomi model is still a time-consuming task. To overcome this issue, we design a novel, hierarchical approach, based on i) adaptive sparse grids quadrature (ASGQ), and ii) quasi Monte Carlo (QMC). Both techniques are coupled with Brownian bridge construction and Richardson extrapolation. By uncovering the available regularity, our hierarchical methods demonstrate substantial computational gains with respect to the standard MC method, when reaching a sufficiently small relative error tolerance in the price estimates across different parameter constellations, even for very small values of the Hurst parameter. Our work opens a new research direction in this field, i.e., to investigate the performance of methods other than Monte Carlo for pricing and calibrating under the rBergomi model. Motivated by the statistical analysis of realized volatility by Gatheral, Jaisson and Rosenbaum [20] and the theoretical results on implied volatility [2,18], rough stochastic volatility has emerged as a new paradigm in quantitative finance, overcoming the observed limitations of diffusive stochastic volatility models. In these models, the trajectories of the volatility have lower Hölder regularity than the trajectories of standard Brownian motion [4,20]. In fact, they are based on fractional Brownian motion (fBm), which is a centered Gaussian process, whose covariance structure depends on the so-called Hurst parameter, H (we refer to [26,16,11] for more details regarding the fBm processes). In the rough volatility case, where 0 < H < 1/2, the fBm has negatively correlated increments and rough sample paths. Gatheral, Jaisson, and Rosenbaum [20] empirically demonstrated the advantages of such models. For instance, they showed that the log-volatility in practice has a similar behavior to fBm with the Hurst exponent H ≈ 0.1 at any reasonable time scale (see also [19]). These results were confirmed by Bennedsen, Lunde and Pakkanen [8], who studied over a thousand individual US equities and showed that H lies in (0, 1/2) for each equity. Other works [8,4,20] showed further benefits of such rough volatility models over standard stochastic volatility models, in terms of explaining crucial phenomena observed in financial markets.The rough Bergomi (rBergomi) model, proposed by Bayer, Friz and Gatheral [4], was one of the first developed rough volatility models. This model, depending on only three parameters, shows remarkable fit to empirical implied volatility surfaces. The construction of the rB...