Sumberg, who had been the CEO of the Reval Hotel Group for 10 years and owned part of the construction company Koger and Sumberg, bought the building at an auction in July from the city of Tallinn for 9.8 million kroons ($576,000).
Sumberg, who presently runs the Estonian Tourism Board and is a consultant for Prime Minister Mart Laar, was the only bidder for the property.
He said it was going to be his major business concern in the future.
Renovations are expected to begin in 2002 and the hotel, which will include 15 to 20 rooms, is to open sometime in 2004.
Sumberg says he plans to make the hotel the most expensive one in Estonia and will invest up to 30 million kroons in it.
"Why did I buy this? Because I liked it," said Sumberg. "It's beautiful, precious and stately. It's going to be my pet project. I'm not expecting a fast profit from it."
Paul Oberschneider, head of the real estate firm Ober-Haus, which operates two hotels in Tallinn's Old Town, said that Sumberg's hotel is too small to be profitable.
"You need geographic scope and size," said Oberschneider. "Fifteen rooms is a hobby."
Sumberg said that Ober-Haus' hotel Park Consul Schlossle, which is also in a medieval building, is ideologically similar to his plans, but he doesn't see it as a competitor.
The Kolm Ode building consists of three similar three-story houses that were built at the beginning of the 15th century. The biggest house was built around 1415 and the smallest one in 1451.
The triplex, which once belonged to three families, was turned into a one-family building after the son of one of the families and the daughter of another were married, said Sumberg.
The building has been reconstructed several times and belonged to several owners. It has a baroque door dating from 1651. The facade was partly changed in the 19th century and the inside was rebuilt in the 60s.
Kalli Holland, head of Vana Tallinn, which examined the architecture of the house, said: "I wish the renovation had not taken place in the 1960s. There was a different attitude toward old things at that time. Everything was changed according to the fashion. The wood was painted dark and now we have a lot of work to do to get this paint off."
She said that a nice rococo painting with two angels was found on the ceiling during the renovation a few weeks ago. Sumberg said that he was happy about the discovery, which he would like to expose to his guests.
"I hope the hotel will have a room with such a function that many people can go there and see the building from the inside," said Holland.
Holland is happy about the investment being made in the building because it was in a run-down condition.
"It was gorgeous from the outside but disgusting from the inside," she said.
Juri Kuuskemae, a curator at the Foreign Art Museum, said that he had dreamed of establishing a "citizen's house" museum in the building, where people could get a glimpse of life in medieval times.
"Rakvere and Tartu have such museums, but we miss it in Tallinn. The city of Tallinn isn't rich enough to afford it. There are a lot of other medieval buildings in Tallinn where we could carry out this idea," he said.
One-third of the buildings in Tallinn's Old Town were built in medieval times, many serving as homes for the city's merchants.
"These houses were built according to a single scheme," said Holland.
The first floor was usually used as a business room and there was a door with a hook for hoisting bags onto the top floor. You can't find similar buildings anywhere else in Estonia because of the destruction caused by frequent wars and fires.