ored to the floor by a pivot and melted metal. This skeleton of pillars was raised up to the second floor, and the pillars were connected, at the top, by big arches made with 2 feet long bricks, placed in order to allow the construction of many rampant vaults, which together constitute the big caveat, destined to support the marble seats (Wilkinson 9). In this way the works could be carried on above and below the cavea at the same time, leaving only some vaults open for the lifting up of the materials. The travertine blocks were all connected to each other by iron clamps, which have long disappeared and have left the holes one can see everywhere. It has been calculated that 300 tons of metal were used only for this purpose. The upper external wall shows that many of the travertine blocks were recycled from other buildings: their internal face is in fact irregular, and they have been leveled only on the external and contact sides. It is undetermined if the wall was constructed in this way so as to save time or if these irregularities depend on later restorations. The external wall was once coupled and supported by a thick brick facing; it is a mystery how the wall you see can still stand. The construction utilized various types of materials that were common for the time: concrete for the foundations, travertine for the piers and arcades, tufa infill between piers for the walls of the lower two levels, and brick-faced concrete used for the upper levels and for most of the vaults. The Coliseum was designed to hold 50,000 spectators, and it had approximately eighty entrances so that crowds could arrive and leave easily. The plan is a vast ellipse, measuring externally 188 m x 156 m (615 ft x 510 ft), with the base of the building covering about 6 acres (Cichy 76). Vaults span between eighty radial walls to support tiers of seating and for passageways and stairs. The facade of three tiers of arches and an attic story is about 48.5 m (158 ...