Oak wood used to build a box around a water well has been dated to about 7,275 years ago, making it the oldest known tree-ring dated wooden structure. The well was discovered near the Czech Republic town of Ostrov in 2018. Ceramic fragments found inside the well dated the site to the early Neolithic, but no evidence of any settlement structures were found nearby.
     Consisting of four oak poles, one at each corner of a roughly 80 by 80 centimetre square with flat planks between them, it stood 140 centimetres above ground. The preservation is exceptional, showing marks from the polished stone tools used to shape each piece with great precision.
     Parts were made from trees were felled in 5255 and 5256 BCE, but two of the poles were felled earlier - one around 7,278 or 7,279 years ago and the other around nine years before that - and must have been used previously. One of the side planks also had a different age - quite a bit younger, felled between 7,261 and 7,244 years ago - likely because of repairs to the well.
     There are over 40 such wells known in Europe dating to a similar period. Some are thought to be earlier, and two of those are in Hungary. One is suspected to be from between 5400 and 5200 BCE and another between 5600 and 5400 BCE, but these have not been tree-ring dated.

Edited from Science Alert (3 February 2020)