On a previous visit I was told that this is a "folly" but today I realised that is [was] a shell house. It would appear that it was decorated with shells inside rather than outside.
A shell is usually a small building, of distinctive shape, and decorated with sea shells. The degree of decoration can vary, from simple lines or features, to a full wall and ceiling covering. Time consuming to make, expensive now to maintain and restore, they are always going to be a rarity.
The East Quad is the first TU Dublin building that you come across after alighting from the LUAS at the new Broadstone plaza that connects to the University via an open, paved walkway.
