Between 11 and 25 March, Swiss artist Felice Varini and his team created an unusual piece of public art that is set to baffle and fascinate visitors to Cardiff Bay barrage.
The piece, entitled 3 Ellipses for 3 Locks, was commissioned by arts agency CBAT for the Cardiff Harbour Authority and cost £25,000.
A series of three yellow ellipses have been painted onto the working locks, gates and even the outer sea wall to create a piece that took a year to plan.
The artist used photography, projection and painting to plan the piece which is his first in Wales and also his first work in the UK.
Professional mountain climbers were required to access the barrage's difficult high structures. The piece was designed to highlight the main working parts of the barrage.
The Harbour Authority approached CBAT to commission the piece, which compliments another 30 open air art projects dotted around the bay area.
From virtually every angle the marks look like splashes of yellow colour against the backdrop of the Penarth headland and the Bristol channel.
But on closer inspection visitors to the Barrage are treated to a visual spectacle featuring three perfectly formed yellow ellipses.
All you have to do to see Felice Varini's 'anamorphic illusion' properly formed, like in the above picture, is find a precise vantage point somewhere on the barrage.