Activist investor Land & Buildings says it's bought 4.3% of iconic Canadian retailer Hudson's Bay Co. and believes the stock is worth many times its current price based on its extensive real estate holdings, and the fund wants the company to take action to realize that value.

The company, said Land & Buildings in a letter to Hudson's Bay, called the company, "one of those rare diamonds in the rough that a real estate investor occasionally finds in a career, where the value of the real estate, which the Company estimates is worth C$35 per share, could be worth 4 times the current share price of C$8.88. Even if the real estate is worth half the Company's estimate, the shares would still be worth double today's share price," it wrote.

Land & Buildings' strategy includes taking the retailer private or redeveloping its vast real estate holdings.

The fund delivered the letter to Hudson's Bay's board Monday morning. The activist investor has suggested selling some of the retailer's prime real estate to be developed into hotels or office buildings.

Insiders own about 20% of the company, making any battle Land & Buildings wants to wage an uphill one.

In his last activist campaign Land & Buildings' chief Johnathan Litt failed in his effort to install two dissident directors onto the board of Taubman Centers (TCO) - Get Report an annual meeting June 1, a major blow to the insurgent manager's push for a sale of the shopping mall operator.

A key impediment was the Taubman's family's large 30% economic and voting interest in Class B shares, according to Litt. The family, which had been fighting against Litt and his fund, Land and Buildings Investment Management, appear to have voted their entire stake for the incumbent directors.

Hudson's Bay, which owns Saks Fifth Avenue and Lord & Taylor, has unsuccessfully explored the purchase of Macy's (M) - Get Report and Nieman Marcus this year. The company announced this month plans to cut 2,000 jobs in North America.

Hudson's Bay Co. is one of the oldest public companies and was once the world's largest landowner, holding about 15% of what is now the U.S. and Canada.

The company received a Royal Charter from the English king in 1670.