Contractors are being invited by Lancashire Wildlife Trust to bid for the £4.75m contract to build facilities for the proposed 250-acre Brockholes wetland and woodland park outside Preston.
The visitor centre will be made up of a number of timber framed structures comprising shop, office and reception, conference facility, café and catering kitchen, teaching facility and exhibition space built on a floating pontoon set on an existing lake.
The nature reserve will be created out of a former gravel quarry and was designed by Adam Khan Architects.
Grant funding of £8m was approved by the North West Development Agency last week.
The attraction is expected to open in 2011.
Deadline for expressions of interest in the build contract is 1 May.