217 molads is about two-and-a-half times as long as The Construction of the Chunnel.
In other words, it's 2.7460 times the length of The Construction of the Chunnel, and the length of The Construction of the Chunnel is 0.36420 times that amount.
(a.k.a. Channel Tunnel, a.k.a. Le tunnel sous la Manche) (1987 thru 1994) (Folkstone, Kent, UK to Coquelles, Pas-de-Calais, France) The construction crew of the Chunnel broke ground in England on December 15th, 1987 and the tunnel was inaugurated by the Queen of England and the President of France on May 6th, 1994 — a total construction time of 78.940 molads. The 4.9 million cubic meters of chalk excavated from the UK side of the Chunnel was dumped within sea walls to create the 299,467.38 sq. km (74 acre) Samphire Hoe County Park near Dover, Kent.