Cúpula vs. domo

In Spanish, both 'cúpula' and 'domo' can be translated to 'dome' in English. Although they can often be used interchangeably, some subtle differences exist that often relate to context or usage.

Cúpula

This word is commonly used to describe the architectural feature known as a dome in general, especially the interior part of the dome. It originates from the Latin 'cupula', meaning small cask or barrel
La cúpula de la catedral es impresionante.
(The cathedral's dome is impressive.)
La pintura en la cúpula del museo es una obra maestra.
(The painting on the museum's dome is a masterpiece.)

Domo

'Domo' originated from Greek language, comes from the Latin 'domus', meaning house. This word often refers to a more specific or modern construction that also resembles a dome, such as a planetarium or sports stadium.
El domo del desierto protege a las plantas de las condiciones extremas.
(The desert dome protects plants from extreme conditions.)
El nuevo estadio tiene un domo retráctil para permitir la entrada de luz natural durante el día.
(The new stadium has a retractable dome to allow natural light in during the day.)

Summary

'Cúpula' and 'domo' both indicate the same architectural feature (dome) in Spanish language, although 'cúpula' tends to refer more generally to any type of architectural dome including classic examples like those found in cathedrals, while 'domo' tends more towards modern and specific constructions.