Complex sentence: The layout of both first and second levels was modified, with the space available for visitors on the second level increased by removing the hydraulic reservoirs that had powered the lifts, hydraulic power being provided by pressurised accumulators at the base of the tower.
Split into simpler sentences: The layout of both first and second levels was modified, with the space available for visitors on the second level. Hydraulic pressure was provided by pressurised accumulators at the base of the tower.