Detail of the painted transept vaults of the Basilica of Saint Servatius in Maastricht, the Netherlands. The keystones are decorated with 5-pointed stars (coat of arms of the city of Maastricht), the key of Saint Servatius and the bifaced eagle, both in the coat of arms of the chapter of Saint Servatius.
<a href="//commons.wikimedia.org/wiki/User:Kleon3" title="User:Kleon3">Kleon3</a>
CC BY-SA 4.0
<span class="int-own-work" lang="en">Own work</span>