MEXICO CITY (AP) — Activists in Mexico have published photos of steel and cement pilings from a government project that were driven directly through the roofs of sensitive limestone caves on the Yucatan peninsula.

The network of caves, sinkhole lakes and underground rivers along Mexico‘s Caribbean coast are both environmentally sensitive and have been found to hold some of the oldest human remains in North America.

While officials have touted the train as utilitarian transport for freight and local residents, its only real source of significant income would be tourists. However, given its frequent stops, unwieldy route and lack of feasibility studies, it is unclear how many tourists will actually want to buy tickets.

The train was partly built by the Mexican army and will be run by the armed forces, to whom López Obrador has entrusted more projects than any other president in at least a century.