This Japanese-funded research center is devoted to the identification and restoration of pieces unearthed at the site. The 1300-sq-m facility has a huge cache of items to sort through, and you can watch the restorers at work. Though not strictly a museum per se, it features an excellent gallery on the different materials used by Maya craftsmen.
The center will house the Museo Sylvanus G Morley for an indefinite period while that museum is under restoration.