According to Colliers investment services manager Nick Estephen, the building was being offered through an international expressions of interest process.

"We've had lots of interest, lots of inspections and from all different types of groups," he said.

The 1910 state listed heritage building is on 17,838 square metres at the gateway to Katoomba, between the Edge cinema and the courthouse complex in Civic Place.

Colliers is touting its many possible uses in an information pack sent to prospective buyers, noting it offered "incredible development potential ... due to versatile zoning, heritage incentive clause and huge excess land".

The site has two residential zonings, R1 general residential and R2 low density residential.

"This zoning permits several uses that could be considered on the excess land including backpacker's accommodation, boarding houses, centre based childcare, dual occupancies, function centres, hotel or motel accommodation, place of worship, and much more," Colliers stated.

The former convent also had a previous approval for 122 independent living units on site.

The grand building was built by the Sisters of Charity to house Mount St Mary's College and Convent, which operated as both a boarding and day student school from 1910 to 1974. It features elaborate great hall rooms, chapel, classrooms, residences, bell tower and outdoor courtyards.

In the 1980s it was converted into the Renaissance creative arts centre, which closed in the 1990s.

It sold in February 2014. At one stage the owners were living in one renovated part of the building but much of it has fallen into disrepair.

Greens candidate for Ward 1, Sarah Redshaw, said the state government should offer some funding to purchase and restore the building for council to operate as a multipurpose site.

She said it could be suitable for tertiary education, a gallery and performance spaces or as an extension of the planned Institute for Planetary Health at Katoomba golf course.

Colliers International believes it could sell for more than $6 million. Expressions of interest close on April 1.

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