A new extension and bird hide for a nature reserve at Whittlesey near Peterborough is being officially opened this week.
Conservation groups and volunteers who helped turn the former brick clay pit into Kings Dyke nature reserve will attend the opening on Thursday.
The reserve is home to at least 141 species of bird, 19 different species of dragonfly and 25 types of butterfly.
Water voles, otters, red deer and grass snakes are also seen at the site.
The site is particularly important for its invertebrates, with more than 1,000 species recorded. The range of rare and declining species makes this site of national importance for its invertebrates.