Chetumal ("place of abundant red cedar" in Maya) is the capital of Quintana Roo, founded in 1898 on the shores of the bay that shares its name. The city itself is not a showstopper, but its position at the end of the highway south from the Yucatan Peninsula — right on the border with Belize — means plenty of travelers pass through and often end up staying longer than planned.
The standout sight is the Museo de la Cultura Maya (Tues–Sun 9am–7pm; US$4), on Héroes near the corner of Mahatma Gandhi. Original artefacts are few, but the interactive displays and scale models do a solid job of explaining ancient Maya society, mathematics, and cosmology — worth a couple of hours before or after crossing the border. Add an evening stroll along the Boulevard Bahía and a quick visit to the Maqueta Payo Obispo, a wooden scale model of the city as it was before a 1955 hurricane flattened it.
Chetumal makes a decent base for day trips to nearby beaches, the Bahía de Chetumal — one of the few places in Mexico where you can still see wild manatees — and Maya ruins scattered across the surrounding jungle.