Part of the remains of the old city wall built in Ming Dynasty.

There use to be a railway line running along the wall, and this was the Signalling station.

Close up of the walls. There are restoring it using old bricks from old houses.

Another view of the South-east tower.

They dug this arch in the wall to let the railway through.

View from under the South-east tower.

The Celestial Globe at the Ancient Observatory.

The Quadrant.

The Ecliptic Armilla.

The Equatorial Armilla.

The Sextant.

The Altazimuth.