It is one of the tallest buildings in London and is being used so that believers can see over the whole city when they pray.
Andy Frost, from Share Jesus International organised the prayer service, and told Premier it is so that people can take time to reflect on the city and speak to God: "it is easy know our own opinions, but it's important to think about others: "It's really important to allow God to speak to each of us, asking what is He already doing, how can we gather and join in with His mission?
"And when we're engaged in mission or in transforming and changing society, we often come with our own opinions and ideas - but actually this is about seeking God, and asking God what are his ideas, what does He get up to, how can we partner with him more effectively in seeing people's lives transformed and changed in this great city?"
He told Premier that this prayer gathering is about creating space for reflection around the question, "How can we join in with what God is doing in this city?"
Mr Frost added that he hopes people will leave and "find a high vantage point in their own community and gather people locally to pray over their own borough and to find what God might be saying to them."
Listen to Premier's Hannah Tooley speak to Andy Frost here:
