As the modern city is built over what was a major pre-Hispanic metropolis, a large part of the area has been designated as an archeological heritage site. However, only six of the declared as such have been investigated as most of the land is privately owned. This includes the Pyramid and some areas under streets where water pipes and sewerage have been modernized. There is opposition to further exploration by many residents as they are concerned that the excavation will cause inconvenience, expropriation of their lands or that the excavated areas will be subject to vandalism.