Are there any man-only places in the world?

All stadiums in Iran are man-only places and women do not have a permission to come in and watch games like football, volleyball, or basketball if the game is between men teams.

All beaches of Persian Gulf and on Iran side of the Caspian sea are man-only for swimming except for women who have complete Islamic cover. There are also some small places for women to swim with swimsuits and men are forbidden to come in.

Sabarimala, a Hindu pilgrimage/temple in Kerala, India, does not allow women between the ages of 10 and 50 (or more precisely the entry of the women in the menstrual age group) to enter the temple. Essentially, this is due to the fact that Ayyappan (the God of Sabarimala) is a Bramachari (Celibate).

The Melbourne Club is a private men's only club in Australia. This is not the kind of thing you would visit as a traveller though. But, considering the people who have been a part of this club, it does highlight how sexism affects the power-balance even in a relatively enlightened country like Australia.

There are undoubtedly hundreds of other similar institutions, etc. that would be male-only or also female-only access. The question as it stands is probably overly broad as a result.

The Herbertstraße "Herbert street" in Hamburg (only in German). It is a street where prostitutes are offering themselves to suitors, sitting in the windows. The street itself has screens so noone outside can look into the street.

There are red signs which prohibit to enter the street for minors and women. While in former times both minors and women were in fact forbidden, legally women should be able to enter the street because it is a public place.

It is still strongly recommended that womens do not enter because the prostitutes will act extremely aggressive. That means jeers, taunts, insults and in some instances a bucket with...fluids on the head. I do not know if this only a rumor to scare women away and in fact it is only water, but some insist that the prostitutes have really used excrements.

There are lots of places in Japan. Here is a list on wikipedia. Among others, this mountain is one of the most strict one.

From the wikipedia article:

Traditionally, women in Japan were not allowed to climb mountains sacred to the Shinto religions. [...] a sign at the entrance to the mountain proclaims "No Women Admitted," in English and Japanese. [...] The ban has been challenged many times but without success. Supporters note that sexual segregation does not equal sexual discrimination.[6] Supporters also state that the ban has an unbroken, 1,300-year tradition.[7] Mount ?mine's designation as a World Heritage site by UNESCO was seen by critics of the ban to have given the gender ban a stamp of approval.[8]

Schorem is a barbershop in Rotterdam (The Netherlands) which allows men and dogs, but is not accessible to women. This is stated on their front page.

Probably other barbershops exist with the same rule, but their webpages do not state it explicitly.

_{I'm not affiliated with Schorem, just thought it would be a valid answer.}

There is an article on exactly that on Fox News: No Women Allowed. In addition to the Mount Athos there is Mount Omine and a few others.

I am not sure where this is but it's still prohibited to women

Two years on :-).

In Australia the Aborigine people designate areas which are for "men's business" (their terminology) and others which are for women's business and each are solely for the designated gender. It is also exceedingly unlikely that you will be admitted to these places (even though of the correct gender) if you do not have at least some Aborigine blood and identify as a member of a 'tribe'.

The right to exclude people of ethnicity or gender from such areas is arguably questionable under some aspects of Australian law but is actively supported and encouraged by Australian government agencies who have regular dealings with the Aborigine people. Generally the reasons given for exclusion of various people are not spelt out and reasons that are given in government brochures are more often than not specious (based on what I have read and then asked about at various locations). The reason for obfuscating a clear government backed policy is not clear (or, not made clear).

In recent decades significant arrangements have been made to access to a wide range of areas to reinforce the enforcement of traditional Aborigine claims to certain specific areas or type of areas.

eg the road around Uluru (aka Ayer's Rock) has been rerouted in places so as to be a significant distance from Uluru in certain places. Notably there is a Women's area at the Western end (if I have my mental topography correct) which is signposted as off limits to all except Aborigine women and the road has been rerouted by about 1 km+ (I think it is) to avoid being near this area.

In some scenic reserve areas (eg "King's Canyon") where it would seem logical for a track to proceed up a gorge to meet a loop track that goes around the canyon. There is no signage and nothing (AFAIK) in the tourist brochures - just a track end at a picturesque viewing platform and a rugged trackless gorge beyond. If the curious (I'm definitely that) were to inquire that may be told (as I was) that the upper end of the gorge is a men only area and that women or any non-Aborigine people are permitted access to that area.

Access to Kata Tjuta (aka "The Olgas") (geologically connected to Ayers rock by a subterranean inverse arch of rock) is a sacred men's area. At one time there was track access throughout the area and a surrounding road. Today the road has gone and the tracks barely penetrate the area.

For example here it says

• Some of these domes are so sacred to the Aboriginal Anangu people that they can't be accessed by non-indigenous people. Aboriginal lore dictates Kata Tjuta is a sacred men's site, and has only two places where non-initiated men can enter. Fortunately there are still enough beautiful walks: the most popular being the Valley of the Winds, Lookout Walk and Olga Gorge

It mentions two entry points amongst the seven domes spread over many miles. ie the very large majority of the area is restricted to access by Aborigine men.

Kings Canyon is also mentioned on the above page but the existence of an out of bounds area is not mentioned.

See also Sacred land

The majority of the above mentioned changes in Australia in recent decades are closely linked to the 1992 Australian Supreme Court Mabo decision - both far too broad a subject and outside the scope of the present question to enter into here. A web search on "Mabo decision" and similar, perhaps starting here will keep you amused for a very very long time if of interest.