The Greek-style frontage is an unusual feature of the chapel
A chapel in Tremadog, Gwynedd - one of five Grade I listed non-conformist chapels in Wales - is to be restored in time for its 200th anniversary.
The main feature of Capel Peniel, a Greek-style frontage, is currently said to be in a dangerous state.
No weddings or funerals can be held in the building because of health and safety concerns.
The chapel was commissioned by Porthmadog town's designer William Alexander Maddocks, and built in 1810.
Tremadog and Porthmadog are built on land reclaimed from the sea by the building of embankments or cobs.
There was a grand scheme to make Tremadog and the Cob in Porthmadog an instrumental part of the London to Dublin route.
But Maddocks' plans relied on Porthdinllaen, near Nefyn, being the favoured departure point for Dublin and in 1810 the decision was made to concentrate on Holyhead instead.
Tremadog grew substantially, however, and by the time Peniel opened its doors in 1810 around 300 people lived there, said the Reverend Gareth Edwards, who looks after the chapel.
"Maddocks was an MP and was familiar with St Paul's Chapel in Covent Garden in London which the architect Inigo Jones copied," Mr Edwards said.
The inside of the chapel is also slightly different because it is set out as a "theatre" on a gradient.
"It means that when I stand in the pulpit my mouth is the same level as the ears of the people sitting at the back, there is no public address system, and it is an easy place to listen and hear."
Otherwise the setting is very traditional for a Calvinistic Methodist chapel, and he added: "It is a little like stepping back in time".
"Because of the chapel's Grade I listing we will get a grant from Cadw [the Welsh historic monuments body] towards the work which will cost upwards of £70,000 but we still need to raise about £40,000 of that ourselves," Mr Edwards said.
The other non-conformist chapels in Wales with Grade 1 listing are Maesyronnen United Reformed, Glasbury, Powys; Tabernacle, Morriston, Swansea; Jerusalem, Bethesda, Gwynedd, and Capel Newydd, Llanengan, Gwynedd.