Further additions and alterations to Clackmannan Tower were made in the 16th and 17th centuries with a wide scale-and-plat staircase being installed leading from the ground floor to the first floor, replacing the original south turnpike stair.

It was also during this time that the tower became fully glazed, and corbelled battlements and machicolations (alternate holes in the stonework), where stones or burning objects could be thrown down onto attackers, were added, and the entrance was arched with a beautiful pedimented frame, with a tree carved in the recessed triangular space at its centre.

This doorway, framed by fluted Doric pilasters, led to a pend that in turn led to a door at the west end giving direct access to the late 17th century mansion house, which was built onto the side of the tower, facing south-west.

Formal access to the upper storeys was via a scale-and-plait stair which was built on the west side of the south wing.

The mansion house had distinctive crow stepped gables and turrets to the south-west with a walled protected entrance court complete with motte to the east.

It remained a family residence until November 1791 when Catherine Bruce died without issue. Her late husband Henry Bruce, a direct descendant of King Robert Bruce, had died 19 years previously.

The estate was bought by Lawrence Dundas, 1st Earl of Zetland (Shetland), but the tower and house were abandoned.

The mansion fell into disrepair and was eventually demolished with some of the stone reputedly being used in new buildings in the town itself.

In 1948, the parts of the eastern walls collapsed due to mine workings with further falls during the 1950s.

By 1966, there was serious concern that the tower would be lost; however, the Ministry of Works set to work and managed to save the medieval building. Damage to the foundations of the tower has caused the entire structure to lean at an angle towards the south.

Remains of the outer walls of the mansion house, a terraced garden, and an ancient bowling green can still be traced.

In 1954 the tower was handed over to what is now known as Historic Environment Scotland and is only open to the public on rare occasions, although this will hopefully change in the near future.

The tower can be seen for miles and has commanding views over the surrounding countryside.

It was category A listed on June 9, 1960, with the tower we see today being the one largely built by the Bruce family.