The present city centre is built on an almost level flood plain just 12 m above sea level. The surface was formed of gravels deposited by melting glaciers at the end of the last Ice Age. The bedrock beneath the gravels is a red mudstone deposited in the late Triassic Period about 220 million years ago.

Toward Cardiff Bay, south of the main railway line, the gravels are covered by estuarine alluvium (mud) which is up to 10 m thick. This mud has been deposited since the last Ice Age when areas have been flooded during high tides. In fact most of Cardiff Bay and the area of Cardiff west of Westgate Street has been built on reclaimed land.

The Civic Centre and Gorsedd Gardens were established around 1905 when Cardiff was declared a city. The Gorsedd Circle was erected originally in 1899 for the Eisteddfod that was held in Cardiff that year.

The stones of the circle are Triassic breccia - formed as an alluvial fan by a large desert river to the north of Cardiff about 220 million years ago and contain grey limestone fragments which are about 250 million years old. These stones were probably quarried in Radyr or Llandaff.

Park House was built between 1871 and 1875 by William Burges for the Marquis of Bute's Agent James McConnochie. The walls are Pennant Sandstone, while the quoins around the windows and entrance porch are Bath Stones. The plinths and string course are coarser ragstones from Bath while the pillars are pink Peterhead granite from Aberdeenshire. The flagstones in the driveway are Pennant Sandstone.

The City Hall, Law Courts and Museum were built in 1904/05 using Portland Stone - a popular material for civic buildings at that time. Wandering around Cardiff, you will notice that many of the older buildings are built from a mixture of Peterhead Granite, Portland Stone, Bath Stone, Radyr Stone and Pennant Sandstone.

Listen out for nearby mistle thrushes, which are often found nesting along Museum Avenue feeding on the fruits of the nearby yew trees.

Turn left back towards the museum, left into Gorsedd Gardens Road, and continue past the museum as far as the Boer Wars Memorial at the top of King Edward VII Avenue.