An alternative method for exploring energy landscapes is the threshold algorithm, which we recently extended to molecular crystals. This algorithm, based on Monte Carlo (MC) simulations, estimates energy barriers between minima on a continuous energy surface using discrete energy thresholds, also called lids. An initial point on the landscape is required as the starting configuration for each threshold simulation, from which a random walk is initiated with steps being accepted strictly if the energy of the resulting configuration is below the current energy threshold. In the case of molecular crystals, the available MC moves include molecular translation and rotation, as well as unit cell changes. Due to the energy threshold, the trajectory of the random walk is constrained to explore only minima that can be reached by a path wherein the maximum energy barrier is less than the threshold energy, and in this way, when a new structure is discovered from energy minimizing an accepted structure, the upper limit of the corresponding energy barrier between it and the initial structure can be estimated as being within the current threshold energy. The threshold energy can be increased iteratively, the previous energy threshold then becoming a lower bound on estimated barriers thereafter. The connections between structures identified from threshold simulations can be concisely conveyed by a disconnectivity graph, which groups minima into basins based on their energy barrier from the initial structure or structures.