Belize is small enough that a Maya temple at breakfast and a reef dive the next afternoon is an ordinary itinerary. Inland, the Cayo District has jungle lodges on the Macal River and Caracol, the largest archaeological reserve in the country. Offshore lies the reef, with three atolls beyond it.
It suits couples and families who want adventure without long transfers, and English is the official language. We usually split a trip between Cayo and one of the cayes or Placencia, using short domestic flights.
The honest caveats: it is a long journey from the UK, with a change in the US, and the lodges are comfortable rather than grand. Rainy season runs from June to November, and the water on the reef is clearest in the dry months.