The limestone corridors beneath the Cayo District have carried water for three million years, carving cathedral chambers the Maya called Xibalba — the underworld. Above ground, the same karst topography created a canopy dense enough to harbour jaguars and scarlet macaws, and tall enough to string zipline platforms thirty metres above the forest floor. San Ignacio sits at the confluence of these two geographies, making it the only place in Central America where you can spend a morning gliding through emergent rainforest and an afternoon floating through subterranean rivers on the same booking. The cave tubing tradition began in the 1990s when archaeologists mapping Actun Tunichil Muknal discovered that inner tubes — originally used by river guides on the Macal — could navigate the low-clearance passages where rafts could not. By 2003, operators had formalized the route through Caves Branch, a tributary system honeycomb with swim-through tunnels lit only by headlamp. The Maya deposited ceremonial pottery in these chambers between 200 and 900 CE, and the darkness preserves calcite formations undisturbed for a millennium. The 40 BZD conservation fee, introduced in 2015, funds both trail maintenance and artefact monitoring by the National Institute of Culture and History. Zipline courses arrived later, built by Costa Rican engineers who recognized that Belize's cohune palm and mahogany stands could support canopy tours without the tower infrastructure required in drier climates. The longest lines stretch 180 metres, high enough to see the Maya Mountains to the south and low enough to make out morpho butterflies in the mid-canopy. Most operations run Monday through Sunday from 08:00 to 17:00, with the first departure timed to reach the caves before midday heat raises the interior humidity above comfortable levels. The combination format — zipline first, cave tubing second — exploits the fact that both activities share a trailhead at Mile 32 on the George Price Highway. A single jungle trek serves both, cutting through secondary forest regenerated after Hurricane Iris in 2001. The soil here is thin, so exposed roots create natural handholds on the steeper sections. Howler monkeys vocalize most reliably between 06:00 and 09:00, which is why guides recommend arriving in the first morning window. The return hike follows the river, past ceiba trees the Maya considered portals between worlds — an engineering coincidence that makes the route feel like a deliberate narrative arc from sky to stone to water.