University Boat Race Stones
The University Boat Race Stones are two tapered, granite cuboids on southern embankments of the Tideway in west London, one 129 metres (423 ft) west of Putney Bridge and the other at Mortlake, 112 metres (367 ft) east of Chiswick Bridge. The stones define the starting and finishing points of the Championship Course.
Source: Wikipedia — University Boat Race Stones (CC BY-SA 4.0)