Still point in time

The Silence exploited the still point in time that was Lake Silencio to engineer the Doctor's death. (TV: The Wedding of River Song)

You may be looking for the Point of Stillness.

According to Dorium Maldovar, still points in time made it easier to create fixed points in time. The Kovarian Chapter of the Silence used one such point in space-time — 5:02 PM on 22 April 2011 by Lake Silencio — to make the Eleventh Doctor's supposed death there a fixed point.

Instead, the Silence merely assumed the Doctor died at Lake Silencio without realising he could and would find a way to fake his death thanks to the time-travelling vehicle the Teselecta, allowing him to survive. (TV: The Wedding of River Song)

These were also known as points of stillness. (AUDIO: Signal and I'll Come to You ^[+]Loading...["Signal and I'll Come to You (audio story)"])