Reconnaissance — Quintana Roo, Mexico
June 2025

The reasoning. LIDAR survey keeps revealing sacbeob between Maya centres that nobody had recorded, the Cobá–Yaxuná causeway being the best-known case. Cobá is a zone I know well. There are two lagoons there, one in front of the site and one to the side that is largely closed to visitors, and a sacbe runs along that lake edge before disappearing into the forest. The assumption was simple: if some causeways run further than we know, this one might too.

The method. You cannot see a sacbe once you are standing on it. What you can do is align with the restored section INAH has cleared, lock a compass bearing, and walk. My training is partly in cave diving, and the logic transfers: it is an in-and-out mission governed by time rather than distance. You walk a bearing for a fixed duration, and you turn back before the reserve is gone. Under canopy the phone rarely updates, so position is dead reckoning. A ninety-degree turn to investigate something off the line is a serious decision — there is no way to count paces accurately enough to find an invisible bearing again.

Four hours out, with a friend. Not an archaeologist.

The find. Quintana Roo has almost no natural relief, so a hill is a signal. Archaeologists taught me how to read a montículo, and once you can see them you find hundreds — in Sian Ka'an there are whole cities you can reach on a 250cc. Most have no opening at all; sometimes half a wall survives. This one read as a thick wall in the forest, ten metres high and more than five wide, built of assembled stone in terrain where there is no stone to fall from. If you did not know what you were looking at you would take it for a mound of earth.

It had a cut rectangular opening with square corners, roughly [1.5 m × 0.5 m].

Inside. A shallow entry of about a metre, then rock descending some four metres to a final shaft. The way on was 30 to 60 cm and largely blocked; I did not pass it. Recording was done from the first hall, capturing the cavity and partially the space beyond.

Limestone throughout, and the coursing was unusual — the largest blocks at the top, some two metres by one, with smaller stone beneath and medium blocks below that. It is the opposite of what you normally see. The form read as rectangular, possibly a collapsed vault, but not the corbel profile I know from elsewhere. What made it clearly built rather than geological was the architecture: coursed blocks and openings between chambers.

Air dense and humid, almost still, with a small cold draught coming from the inner chamber through a vent the size of a single block, 20 to 25 cm. Bats, insects, reptiles. Frogs and mosquitoes at the entrance.

The capture. Zoom H1 with a hypercardioid mic. Stereo for the hall, hypercardioid into the shaft and toward the inner chamber. Excitation by hand and by phone through a small speaker: claps, whoops, bursts, clicks, short sweeps. Nothing long — these were first attempts, and we were already out of time.

The exit. We had pushed past the point where we should have turned back, and we recorded when we should already have been walking. The return cost us. We were caught by the night, took some damage getting through it, and reached the car hours late with no camp, no net, no water left. We ate very late in Tulum, and were glad to be intact. The recording was worth having; the timing was a mistake, and I would not repeat it.

What came of it. These became the first impulse responses I worked with, and they changed how I compose. The high-frequency content was unlike anything I expected — the chamber was not a single resonance but a full resonant body, complex enough to modulate other material rather than simply colour it.

It also ended something for me. I had been working near the solfeggio frequencies, the way a lot of people in this field do. Running the analysis on these responses made that untenable. What a chamber does to sound is not one number. It is a dense, position-dependent, phase-sensitive structure, and the claims made for individual frequencies do not survive contact with a real measurement. That shift is the reason this work became archaeoacoustics rather than sound healing.

Status. No excavation, no removal, no contact with structures beyond entering the first hall. The feature is unrecorded as far as I know, and I have no way to confirm what it is. I intend to report it, along with structures closer to Cobá that I could relocate reliably, to Centro INAH Quintana Roo, and would welcome the chance to return under their supervision and record properly.