Mexican vault. photo by Michael Ramage, Scaffolding to structure seminar, Cambridge University. This example was done by unskilled students in a learning process sort of way, but it shows the nature of the brick used.
A very interesting pdf of a Scaffolding to Structure seminar, under Philippe Block and Lara Davis at Cambridge University in 2010, is here. It includes the building of a mexican vault, above, outlined for them by Alfonso Ramirez Ponce, a Mexican architect who lectures at UNAM and teaches low cost sustainable construction using regional materials.
Such vaults are called bovedas; an odd little video, below, shows precisely how they are done in Mexico, by skilled masons:
The Boveda at Casa Chorro from bloodredcolt on Vimeo.