If you’re talking about the construction industry, scale is very important – perhaps more so than in most other industries. This is because of the extraordinary efforts that had to go into making the plans for them into a reality.
Some of the bigger construction projects out there which would most definitely be included in any discussion about mega-construction projects, would be things like building a skyscraper, power station, or Dam. Any of these would require a massive number of building workers on-site to deal with numerous areas of building, and of engineers and architects who’ve made the plans and built the road-map which allow the project to go forward.
Some of the engineering concerns can be far more complicated in big projects than smaller ones. An example of this can be seen with the use of concrete: Concrete can be added with little complicating factors when in small amounts, but when you’re using vast quantities, such as with a dam, the internal mass of the concrete can be so vast that the amount of time required for the concrete to cool down and set is too massive for it to be feasible. This was realised during the planning of hoover dam, where calculations showed that it would take 125 years for the concrete to set, so they instead segregated the concrete to allow portions to be constructed in intervals, reducing the mass of the concrete and therefore the time required for it to cool.